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What is my ship's CII rating?

CII calculator for ships of 5,000 GT and above under MARPOL Annex VI Reg. 28 · MEPC.352(78) to MEPC.354(78), MEPC.338(76) and MEPC.400(83) · Updated 18 October 2026

Published by ShipCalculators.com. Method checked against MEPC.352(78), MEPC.353(78), MEPC.338(76), MEPC.400(83) and MEPC.354(78) on 18 October 2026. How calculators are checked

Answer

Under MARPOL Annex VI Regulation 28, an 82,000 DWT bulk carrier burning 5,600 t of HFO over 60,000 nm attains a CII of 3.544 gCO2 per dwt-nm (MEPC.352(78)) against a 2026 required CII of 3.709 (the MEPC.353(78) reference line less 11% under MEPC.338(76)): a ratio of 0.956, rating C under MEPC.354(78).

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On this page

What the Carbon Intensity Indicator is

The Carbon Intensity Indicator (CII) is the grams of CO2 a ship emits per tonne of deadweight, or per unit of gross tonnage, of capacity for each nautical mile sailed, worked out from a full calendar year of fuel and distance under MARPOL Annex VI Regulation 28 and the CII Guidelines.1,2 Each year the attained figure is compared with a required figure: the reference line for the ship’s type and size, cut by that year’s reduction factor.4,5 The ratio of the two places the ship in band A, B, C, D or E.7

Attained, required and rating for your ship

Worked examples on this page

The ship

Choosing a type loads its worked example; change any figure after. Slider marks: the size-row edges of MEPC.353(78) Table 1 and the 2023 fleet mean from the IMO report on 2023 DCS data, MEPC 82/6/38.

Deadweight at the maximum summer draught, from the stability booklet

The year

Z cuts the reference line: MEPC.338(76) to 2026, MEPC.400(83) for 2027 to 2030.

The operation

From the IMO DCS report for the calendar year.

Distance over the ground in the year, under way and not under way, from the DCS report

HFO burned in the year, Cf 3.114 t CO₂ per t (Heavy fuel oil, RME to RMK, and VLSFO of those grades)

LFO burned in the year, Cf 3.151 t CO₂ per t (Light fuel oil, RMA to RMD, and VLSFO of those grades)

MGO / MDO burned in the year, Cf 3.206 t CO₂ per t (Diesel or gas oil, DMX to DMB)

LNG burned in the year, Cf 2.750 t CO₂ per t (Liquefied natural gas)

Methanol burned in the year, Cf 1.375 t CO₂ per t (Methanol)

Attained CII, gCO₂/dwt·nm, worked out from the fuel and distance

A bulk carrier of 82,000 DWT that sailed 60,000 nm in 2026 and burned 5,600 t of HFO. Rated C against a required CII of 3.709.

CII rating C for 2026: attained 3.544, required 3.709, ratio 0.956

Rating
C
CII rating 20263.544 attained · required 3.709 · gCO₂/dwt·nm

At 0.956 of the required CII the ship rates C for 2026. It can rise by 0.386 before falling to D.

this ship 3.544ratio 0.956, band CEabove 4.376ratio above 1.18D3.931 to 4.376ratio 1.06 to 1.18C3.486 to 3.931ratio 0.94 to 1.06B3.190 to 3.486ratio 0.86 to 0.94Aup to 3.190ratio to 0.86This ship: 3.544

Band edges for 2026, gCO₂/dwt·nm

flat line: 3.544B’23B’24B’25C’26C’27C’28C’29D’30

The same attained CII, rated each year to 2030

HFO to each band edgeto A, edge 3.190−561 tto B, edge 3.486−92 tto D, edge 3.931+611 tto E, edge 4.376+1,314 t
Attained CII
3.544
Required CII
3.709
Attained ÷ required
0.956
Reference line
4.167
Reduction factor Z
11%
CO₂ in the year
17,438 t

All drawings · Cite ·

Cite or share this calculation

ShipCalculators.com. “CII Calculator: Attained, Required and A to E Rating.” Method: MEPC.352(78) as amended by MEPC.412(84), MEPC.364(79), MEPC.353(78), MEPC.338(76), MEPC.354(78). Inputs: bulk carrier of 82,000 DWT that sailed 60,000 nm in 2026 and burned 5,600 t of HFO. Result: attained 3.544, required 3.709, ratio 0.956, rating C. https://shipcalculators.com/calculators/cii.

The citation names ShipCalculators.com as publisher; copying it adds today's date.

CII headroom: what this result means for the ship

At 0.956 of required, the ship is in band C for 2026. Burning about 92 t less HFO in the year (1.6% of the HFO burned) would reach B. It can burn about 611 t more HFO before falling to D. A rating of D for three consecutive years, or E in one year, would require a plan of corrective actions (Regulation 28.7), added to the SEEMP (Regulation 28.8).

CO₂ 17,438 t in 2026HFO17,438 tLFO0 tMGO / MDO0 tLNG0 tMethanol0 t

CO₂ by fuel, the numerator of the attained CII

What a fuel saving does to the rating

A: as entered17,438 t CO₂C3.544Ratio 0.956
B: 8% less fuel16,043 t CO₂B3.261Ratio 0.879
EDCBA8% less fuel: ratio 0.879now 0.956, band C8% less fuel: 0.879, band B0%20% less fuel

The ratio against a fuel saving of 0 to 20%. Every fuel falls by the same share, with distance and capacity unchanged, so the attained CII falls by that share.

CII rating boundaries for this ship

Band edges for 2026, MEPC.354(78) Table 1, applied to this ship's required CII of 3.709
BandAttained ÷ requiredAttained CIIHFO at upper edgeChange
Aat or below 0.86up to 3.1905,039 t−561 t
Babove 0.86, at or below 0.943.190 to 3.4865,508 t−92 t
CThis shipabove 0.94, at or below 1.063.486 to 3.9316,211 t+611 t
Dabove 1.06, at or below 1.183.931 to 4.3766,914 t+1,314 t
Eabove 1.18above 4.376no upper edge

Multipliers 0.86, 0.94, 1.06 and 1.18 for this ship type, MEPC.354(78). HFO tonnes at each upper edge assume the same distance, capacity and other fuels. The highlighted row, marked This ship, is the band the ship is in now.

HFO to each band edgeto A, edge 3.190−561 tto B, edge 3.486−92 tto D, edge 3.931+611 tto E, edge 4.376+1,314 t

Headroom to each band edge, other fuels and distance unchanged

Your ship's CII drawn: the year, the bands and the reference line

The rating ladder for 2026

this ship 3.544ratio 0.956, band CEabove 4.376ratio above 1.18D3.931 to 4.376ratio 1.06 to 1.18C3.486 to 3.931ratio 0.94 to 1.06B3.190 to 3.486ratio 0.86 to 0.94Aup to 3.190ratio to 0.86This ship: 3.544

The same ship, every year to 2030

flat line: 3.544B’23B’24B’25C’26C’27C’28C’29D’30

The year's transport work

82,000 DWT, bulk carrier60,000 nm = 2.78 × 21,600 nm= 3.544 g CO₂ per DWT·nm

CO₂ by fuel

CO₂ 17,438 t in 2026HFO17,438 tLFO0 tMGO / MDO0 tLNG0 tMethanol0 t

What a fuel saving does

EDCBA8% less fuel: ratio 0.879now 0.956, band C8% less fuel: 0.879, band B0%20% less fuel

The ratio on a dial

ABCDEratio 0.956

On the reference line for its type

82,000 DWT: 3.544this ship 3.544 at 82,000 DWTdashed: required 2026, 3.7095,000420,000 DWTABCDE
A bulk carrier of 82,000 DWT that sailed 60,000 nm, 2.78 times a 21,600 nm great circle, and emitted 17,438 t of CO₂, attains 3.544 gCO₂/dwt·nm. The 2026 required CII is 3.709, so the ratio is 0.956 and the band is C. At the same attained figure the ship rates B, B, B, C, C, C, C, D for 2023 to 2030.

CII reduction factor by year, applied to this ship

Required CII for this ship, 2023 to 2030
YearZRequiredRatioBand
20235%3.9590.895B
20247%3.8750.915B
20259%3.7920.935B
202611%3.7090.956C
202713.625%3.5990.985C
202816.25%3.4901.016C
202918.875%3.3811.048C
203021.5%3.2711.083D

Reference line 4.167 for this ship, MEPC.353(78). Reduction factors Z for 2023 to 2026 from MEPC.338(76), and for 2027 to 2030 from MEPC.400(83). The reference line stays fixed and Z cuts it further each year, which is why a rating slips with nothing changed on board.

Year on year: attained CII against the required line

Attained CII in 2025, the previous year's figure to compare against this year's

Attained CII, required CII and rating worked by hand

To find the attained CII, multiply the tonnes of each fuel burned in the calendar year by its CO2 factor (3.114 for HFO, 3.151 for LFO, 3.206 for diesel or gas oil, 2.750 for LNG and 1.375 for methanol, from MEPC.364(79)), add the results and multiply by 1,000,000 to convert to grams.8 Divide by the capacity times the nautical miles traveled in the year, both under way and not under way.2,3 For the required CII of a bulk carrier, raise the deadweight (fixed at 279,000 for ships at or above it) to the power −0.622 and multiply by 4,745, then multiply by one minus the year’s reduction factor: 0.89 for 2026.4,5 Divide attained by required: at or below 0.86 rates A, up to 0.94 B, up to 1.06 C, up to 1.18 D, and anything higher E.7

Worked example with your numbers

A bulk carrier of 82,000 DWT that sailed 60,000 nm in 2026 and burned 5,600 t of HFO. Check each line with a calculator; the last one is the rating in the result box.

  1. CO₂ emitted5,600 t HFO × 3.114 = 17,438.4 tCf, MEPC.364(79)
  2. Transport work82,000 DWT × 60,000 nm = 4,920,000,000MEPC.352(78) section 4.2, as replaced by MEPC.412(84)
  3. Attained CII17,438.4 t × 1,000,000 ÷ 4,920,000,000 = 3.544MEPC.352(78), G1
  4. Reference line4,745 × 82,000^−0.622 = 4.167MEPC.353(78), G2
  5. Required CII, 20264.167 × (1 − 11%) = 3.709MEPC.338(76), G3
  6. Ratio3.544 ÷ 3.709 = 0.956MEPC.354(78), G4
  7. Rating0.956 is above 0.94 and at or below 1.06, so band CMEPC.354(78), G4 Table 1

Values are shown rounded; the calculation carries full precision, so the last digit of a hand check can differ by one.

Formula, assumptions, and limits

An 82,000 DWT bulk carrier that burns 5,600 t of HFO over 60,000 nm in 2026 attains 3.544 gCO2 per dwt-nm against a required 3.709, a ratio of 0.956 and a C rating. The calculation takes four IMO instruments in turn: MEPC.352(78) for the attained figure, MEPC.353(78) for the reference line, MEPC.338(76) and MEPC.400(83) for the reduction factor, and MEPC.354(78) for the rating.

Formula

The attained CII is the CO2 emitted over the transport work:

CIIatt=∑jFCj CF,j⋅106C⋅Dt \begin{aligned} \text{CII}_{att} &= \frac{\sum_j FC_j \, C_{F,j} \cdot 10^6}{C \cdot D_t} \end{aligned}

The required CII is the reference line for the ship type and size, cut by the year’s reduction factor, and the rating compares the two:

CIIreq=a Cref−c (1−Z)R=CIIattCIIreq \begin{aligned} \text{CII}_{req} &= a \, C_{ref}^{-c} \,(1 - Z) \\ R &= \frac{\text{CII}_{att}}{\text{CII}_{req}} \end{aligned}
  • FCjFC_j: tonnes of fuel jj burned in the calendar year.
  • CF,jC_{F,j}: tonnes of CO2 per tonne of fuel, MEPC.364(79) para 2.2.1, which superseded the MEPC.308(73) that G1 para 4.1 names: 3.114 HFO, 3.151 LFO, 3.206 diesel or gas oil, 2.750 LNG, 1.375 methanol.
  • CC: capacity, deadweight or gross tonnage by ship type.
  • DtD_t: total distance over the ground in the year (MARPOL Annex VI Reg. 2.2.12), nautical miles, under way and not under way.
  • aa, cc, CrefC_{ref}: the reference-line coefficients and the capacity the line uses, MEPC.353(78) Table 1.
  • ZZ: the reduction factor for the year, as a fraction.
  • RR: the ratio, rated against the four MEPC.354(78) multipliers for the ship type.

Derivation

Regulation 28 of MARPOL Annex VI takes the attained annual operational CII from the fuel and distance each ship already reports to the IMO Data Collection System. The CII Guidelines (G1, MEPC.352(78)) define the attained figure as the mass of CO2 over the supply-based transport work, capacity times total distance. MEPC.412(84), adopted on 1 May 2026, replaced G1 section 4.2: it keeps that supply-based figure as the proxy even where actual transport work is reported, and confirms that the distance covers miles both under way and not under way.

The reference line comes from the 2019 fleet: MEPC.353(78) fitted a⋅C−ca \cdot C^{-c} to each ship type, with separate rows for size bands. Regulation 28.4 then sets the required CII as the reference line less Z percent. Regulation 28.6 places the required CII at the middle of band C, and MEPC.354(78) draws the four boundaries as fixed multiples of it, so the band follows from the ratio alone.

Assumptions

  • The fuel figures are the tonnes burned in the calendar year, as reported to the IMO DCS, and the Cf values are the MEPC.364(79) defaults.
  • The attained CII uses the ship’s actual capacity; the fixed capacities of MEPC.353(78) Table 1 enter the reference line only.
  • A ratio exactly on a boundary takes the better band. MEPC.354(78) does not state which band an exact boundary value falls in.
  • Reduction factors run from 2023 to 2030 only; none is adopted after 2030.

Worked example

The 82,000 DWT bulk carrier in the answer, step by step:

StepWorkingInstrument
CO2 emitted5,600 t × 3.114 = 17,438.4 tMEPC.364(79)
Transport work82,000 × 60,000 = 4,920,000,000 dwt-nmMEPC.352(78)
Attained CII17,438.4 × 10⁶ ÷ 4,920,000,000 = 3.544MEPC.352(78)
Reference line4,745 × 82,000^−0.622 = 4.167MEPC.353(78)
Required CII, 20264.167 × (1 − 0.11) = 3.709MEPC.338(76)
Ratio3.544 ÷ 3.709 = 0.956MEPC.354(78)
Rating0.956 is above 0.94 and at or below 1.06, so CMEPC.354(78)

With the same attained figure the ship rates B for 2023 (ratio 0.895) and 2025 (0.935), C for 2027 (0.985) and 2028 (1.016), and D for 2030 (1.083), because the required CII falls each year while the attained figure stays where it is.

Edge cases and limits

  • Size-row boundaries. “X and above” against “less than X” puts a ship exactly at X in the upper row. The reference line jumps at some boundaries: a gas carrier’s line is 6.812 just below 65,000 DWT and 15.523 at 65,000, an LNG carrier’s 6.248 just below 100,000 DWT and 9.827 at it, and a vehicle carrier’s 11.106 just below 30,000 GT and 8.280 at it.
  • LNG carriers below 65,000 DWT. MEPC.353(78) Table 1 prints a = 14779E10 for this row and 14479E10 for the row above, so the line steps from 20.171 below 65,000 DWT to 19.762 at it. The revoked MEPC.337(76) Table 1 printed 14479E10 for both rows, and guidance written from it still does; this calculator uses the figure in MEPC.353(78).
  • The fixed capacities. A 400,000 DWT ore carrier that burns 13,500 t of HFO over 52,000 nm rates against the 1.946 reference line of a 279,000 DWT ship, while its attained CII uses the full 400,000 DWT: 2.021, not the 2.898 it would be with the 279,000 DWT applied to the attained figure too. IACS Recommendation 175 (Rev.1, June 2025) section 7.1 states it: the ship’s actual DWT or GT for the attained CII, the Table 1 threshold capacity for the required CII.
  • Corrections not applied. MEPC.355(78) allows voyage exclusions and correction factors for ice class, shuttle tankers, cargo heating, ship-to-ship operations and electrical consumption, and G5 para 3.2 rates the corrected figure. The calculator applies none of them.
  • High-speed craft. MEPC.354(78) has one ro-ro passenger row, so the high-speed craft line from MEPC.353(78) takes the ro-pax boundaries.
  • Amendments from 2027. MEPC.407(84) amends Regulations 27 and 28 from 1 September 2027, and MEPC.1/Circ.905/Rev.1 changes the carbon factor of a biofuel blend from energy weighting to mass weighting from 1 January 2027. Neither is modeled here.

Regulatory basis

MARPOL Annex VI Regulation 28 sets the obligation; the four guidelines set the numbers. MEPC.352(78), MEPC.353(78) and MEPC.354(78) were adopted on 10 June 2022 and revoked MEPC.336(76), MEPC.337(76) and MEPC.339(76) respectively. MEPC.338(76) of 17 June 2021 set Z to 2026, and MEPC.400(83) of 11 April 2025 replaced its Table 1 to add 2027 to 2030. MEPC.412(84) of 1 May 2026 replaced G1 section 4.2.

Common errors

  1. Using cargo carried, or a commercial deadweight, as capacity. Capacity is the deadweight or gross tonnage from the ship’s particulars, not the tonnes loaded; G1 footnote 1 takes the deadweight at the maximum summer draught certified in the approved stability booklet.
  2. Mixing the capacity bases. A ro-pax or cruise ship rates on gross tonnage; entering its deadweight gives a figure in the wrong unit.
  3. Counting only sea-passage miles. The distance is all the miles over the ground in the year, under way and not under way (MEPC.412(84), MEPC.413(84) para 7.7.2), canal passages included as not under way (MEPC.401(83) para 7.6).
  4. Applying a fixed capacity to the attained figure. The 279,000 DWT, 65,000 DWT and 57,700 GT of MEPC.353(78) Table 1 belong to the reference line only.
  5. Reporting VLSFO under “Other”. The IMO report on 2023 DCS data (MEPC 82/6/38, para 22) found VLSFO and LFO reported under the “Other” fuel category. MEPC.364(79) sets the factor by ISO 8217 grade, so a very low sulphur fuel oil takes 3.114 if it is RME to RMK and 3.151 if it is RMA to RMD.

Where to find the DCS fuel, distance and capacity figures

  • Fuel burned: the annual fuel oil consumption by fuel type that the company reports to the Administration under the IMO Data Collection System (MARPOL Annex VI Reg. 27), built from the bunker delivery notes or flow meter records.
  • Distance: the DCS distance for the calendar year, over the ground, with the miles under way and not under way added together; canal passages count as not under way (MEPC.401(83) para 7.6).
  • Capacity: the deadweight at the maximum summer draught in the approved stability booklet, or the gross tonnage from the International Tonnage Certificate (1969): gross tonnage for ro-ro cargo, vehicle carriers, ro-pax and cruise ships, deadweight for the rest.
  • A verified attained figure: the Statement of Compliance issued after the Administration verifies the DCS data (the Statement of Compliance on fuel oil consumption reporting and operational carbon intensity rating, MARPOL Annex VI Reg. 6.6), which also carries the rating of record.

Regulatory basis

Regulation 28 of MARPOL Annex VI was added by MEPC.328(76) and entered into force on 1 November 2022, with the first ratings for calendar year 2023.1 It applies to ships of 5,000 GT and above of the types it lists, and leaves the numbers to four guidelines, each adopted as an MEPC resolution:

Obligation
MARPOL Annex VI Reg. 28, MEPC.328(76)1
Attained CII (G1)
MEPC.352(78), section 4.2 as replaced by MEPC.412(84)2,3
Distance under way and not under way
SEEMP Guidelines paras 7.6 and 7.7.2, MEPC.401(83) and MEPC.413(84)10,11
Reference lines (G2)
MEPC.353(78) Table 14
Reduction factors (G3)
MEPC.338(76) to 2026; MEPC.400(83) for 2027 to 20305,6
Rating (G4)
MEPC.354(78) Table 17
Carbon factors
MEPC.364(79) para 2.2.18
Corrections (G5)
MEPC.355(78), not applied here9

Revoked CII guidelines and their replacements

RevokedReplaced bySubject
MEPC.336(76), 17 June 2021MEPC.352(78), 10 June 2022CII calculation guidelines (G1)2
MEPC.337(76), 17 June 2021MEPC.353(78), 10 June 2022CII reference lines (G2)4
MEPC.339(76), 17 June 2021MEPC.354(78), 10 June 2022CII rating guidelines (G4)7

Each of the three is revoked by the resolution that replaced it; this page and the calculator use only the replacements.

CII reference line by ship type, MEPC.353(78) Table 1

Required CII reference line = a × capacity^−c, MEPC.353(78) Table 1
Ship typeSizeacCapacity in the line
Bulk carrierbelow 279,000 DWT4,7450.622DWT
Bulk carrier279,000 DWT and above4,7450.622fixed at 279,000 DWT
Gas carrierbelow 65,000 DWT8,1040.639DWT
Gas carrier65,000 DWT and above1.4405 × 10¹¹2.071DWT
Oil tankerall sizes5,2470.61DWT
Container shipall sizes1,9840.489DWT
General / multipurpose cargobelow 20,000 DWT5880.3885DWT
General / multipurpose cargo20,000 DWT and above31,9480.792DWT
Refrigerated cargo carrierall sizes4,6000.557DWT
Combination carrier (OBO)all sizes5,1190.622DWT
LNG carrierbelow 65,000 DWT1.4779 × 10¹⁴2.673fixed at 65,000 DWT
LNG carrier65,000 to below 100,000 DWT1.4479 × 10¹⁴2.673DWT
LNG carrier100,000 DWT and above9.8270DWT
Ro-Ro vehicle carrier (PCTC)below 30,000 GT3300.329GT
Ro-Ro vehicle carrier (PCTC)30,000 to below 57,700 GT3,6270.59GT
Ro-Ro vehicle carrier (PCTC)57,700 GT and above3,6270.59fixed at 57,700 GT
Ro-Ro cargo shipall sizes1,9670.485GT
Ro-Pax (passenger + Ro-Ro)all sizes2,0230.46GT
Ro-pax high-speed craft (SOLAS chapter X)all sizes4,1960.46GT
Cruise passenger shipall sizes9300.383GT

The highlighted row is the one the calculator applies to the ship entered above. A c of 0 makes the line flat: the same required value at every size in that range.

CII, EEXI and EEDI compared

IndexMeasuresBased onMARPOL Annex VI
CIIOperational carbon intensity, rated every calendar yearFuel burned and distance sailedReg. 28
EEXITechnical efficiency of a ship in service, verified once and again after a major conversionEngine power, speed and capacityRegs. 23 and 25
EEDITechnical efficiency of a new ship, at its design stageEngine power, speed and capacityRegs. 22 and 24

The CII can change every year with how a ship is operated; the EEXI and EEDI change only with the ship’s machinery or design.1

What the CII calculator leaves out: corrections, verification and the rating of record

  • The voyage exclusions and correction factors of MEPC.355(78): ice class, shuttle tankers, cargo heating, ship-to-ship transfer and electrical consumption.
  • The rating of record: it is the one in the Statement of Compliance issued after the IMO DCS data are verified, and this calculator’s result is an estimate for planning.
  • Fuel-specific carbon factors other than the MEPC.364(79) defaults, including biofuels; from 1 January 2027 a blend’s factor is weighted by mass under MEPC.1/Circ.905/Rev.1.
  • The amendments to Regulations 27 and 28 in MEPC.407(84), which enter into force on 1 September 2027.
  • Ratings before 2023 or after 2030, for which no reduction factor applies or is adopted.
  • Ships below 5,000 GT and types outside Regulation 28.

How to use this calculator

  1. Pick the ship type card first: it sets the MEPC.353(78) reference line and the MEPC.354(78) rating boundaries, says whether the type is rated on DWT or GT, and loads that type's worked example, or tap one of the worked-example chips above it.
  2. Set the capacity on the slider or in the box: the deadweight at the maximum summer draught, or the gross tonnage, as the card says. The slider is marked where the MEPC.353(78) size row changes and at the 2023 fleet mean.
  3. Choose the reporting year chip from 2023 to 2030; each chip shows its reduction factor Z.
  4. Choose Fuel and distance, then set the distance over the ground in the year (under way and not under way) and the tonnes of each fuel; or choose A figure I have and enter the attained CII from the Statement of Compliance.
  5. Read the rating, the attained and required CII, the band ladder, the rating for each year to 2030 and the headroom to each band edge; the sentence under the inputs reads them back, and the drawings and the fuel-saving slider below show the rest.

Frequently Asked Questions (FAQs)

How is attained CII calculated?

Multiply the tonnes of each fuel burned in the calendar year by its CO2 factor Cf from MEPC.364(79) (3.114 for HFO, 3.206 for diesel or gas oil, 2.750 for LNG), add them and convert to grams, then divide by the ship's capacity times the distance sailed in the year (MEPC.352(78) as amended by MEPC.412(84)). An 82,000 DWT bulk carrier burning 5,600 t of HFO over 60,000 nm attains 3.544 gCO2 per dwt-nm.

What is the required CII for 2026?

The required CII is the MEPC.353(78) reference line for the ship type and size, reduced by the year's factor Z: 11% for 2026 under MEPC.338(76). For an 82,000 DWT bulk carrier the reference line is 4.167, so the 2026 required CII is 3.709 gCO2 per dwt-nm.

What are the CII reduction factors for 2027 to 2030?

MEPC.400(83), adopted on 11 April 2025, set Z at 13.625% for 2027, 16.25% for 2028, 18.875% for 2029 and 21.5% for 2030. The earlier factors under MEPC.338(76) are 5%, 7%, 9% and 11% for 2023 to 2026. No factor is adopted after 2030.

How are the A to E rating boundaries set?

MEPC.354(78) sets four multipliers per ship type and applies them to the required CII. For a bulk carrier they are 0.86, 0.94, 1.06 and 1.18: a ratio of attained to required at or below 0.86 is A, up to 0.94 B, up to 1.06 C, up to 1.18 D, and above 1.18 E. The required CII is the middle of band C (MARPOL Annex VI Reg. 28.6).

What CII rating does a ship need?

Regulation 28 of MARPOL Annex VI sets no minimum band. To avoid a plan of corrective actions, the ship must not rate E in any year or D three years running (Reg. 28.7). The required CII is the middle of band C (Reg. 28.6), so a ship in the upper part of C is already above it, and Administrations are encouraged to give incentives to A and B ships (Reg. 28.10).

Is the required CII the same for every ship of a type?

No. The MEPC.353(78) reference line is a times capacity to the power minus c, so over most sizes it falls as capacity rises: for a bulk carrier, 4,745 × 82,000^−0.622 gives 4.167. The line is flat where Table 1 fixes the capacity (bulk carriers from 279,000 DWT, vehicle carriers from 57,700 GT, LNG carriers below 65,000 and from 100,000 DWT), and it jumps where the row changes: a 64,000 DWT gas carrier's line is 6.879, a 65,000 DWT one's 15.523.

Which capacity does CII use, deadweight or gross tonnage?

Deadweight for bulk carriers, tankers, container ships, gas and LNG carriers, general cargo, refrigerated cargo and combination carriers; gross tonnage for ro-ro cargo ships, ro-ro vehicle carriers, ro-pax and cruise passenger ships (MEPC.352(78) section 4.2). The deadweight is at the maximum summer draught certified in the approved stability booklet. For the reference line only, MEPC.353(78) fixes the capacity at 279,000 DWT for bulk carriers at or above it, 65,000 DWT for LNG carriers below it and 57,700 GT for vehicle carriers at or above it; the attained CII always uses the ship's own figure (IACS Recommendation 175 Rev.1, section 7.1).

Why does my CII rating get worse when nothing on board changed?

The reference line stays fixed, but Z rises each year, so the required CII falls by 2.1 to 3.2% a year. An 82,000 DWT bulk carrier at 3.544 gCO2 per dwt-nm rates B in 2025, C in 2026 and D in 2030 with the same attained figure.

What happens if a ship is rated D or E?

A ship rated D for three consecutive years, or E once, must develop a plan of corrective actions to achieve the required CII and add it to SEEMP Part III, submitted no later than one month after reporting the attained CII (MARPOL Annex VI Reg. 28.7 and 28.8). The CII corrective-plan projector works out the cut the plan needs.

Does the distance include miles sailed while not under way?

Yes. The CII distance is the total distance traveled over the ground in the calendar year (MARPOL Annex VI Reg. 2.2.12), as reported to the IMO Data Collection System. MEPC.412(84), adopted on 1 May 2026, confirms in section 4.2 of the CII Guidelines that this covers miles both under way and not under way, and MEPC.413(84) para 7.7.2 says the same for the SEEMP data. Canal passages count as not under way under para 7.6 of the SEEMP Guidelines, added by MEPC.401(83).

Is a CII reduction factor set after 2030?

No. MEPC.400(83), adopted on 11 April 2025, sets Z only to 2030, at 21.5%, and MEPC.354(78) gives its rating boundaries for 2023 to 2030 (paras 1.1 and 3.2).

Is CII the same as EEXI or EEDI?

No. EEXI and EEDI are technical indices of the ship's design, verified once and again after a major conversion (MARPOL Annex VI Regs. 22 to 25). CII is operational: it is worked out every calendar year from the fuel burned and the distance sailed, and rated A to E each year (Reg. 28).

Test cases this calculator passes

Every build of this site runs these cases through the calculator above and stops the release if any figure moves outside its tolerance. Load a case to put its inputs into the calculator.

InputsExpected resultTraced toLoad
Bulk carrier, 82,000 DWT, 60,000 nm, 5,600 t HFO, 2026Attained CII: 3.544Required CII: 3.709Rating: CMEPC.352(78) para 4.2 (attained); MEPC.353(78) Table 1 (a 4745, c 0.622); MEPC.338(76) Table 1 (Z 11%); MEPC.354(78) Table 1 (ratio 0.956); MEPC.364(79) para 2.2.1 (HFO Cf 3.114)Load inputs
Same ship and fuel, rated for 2023 (Z 5%)Attained CII: 3.544Required CII: 3.959Rating: BMEPC.338(76) Table 1 (Z 5%); MEPC.354(78) Table 1 (ratio 0.895)Load inputs
Bulk carrier, 400,000 DWT, 52,000 nm, 13,500 t HFO, 2026Attained CII: 2.021Required CII: 1.732Rating: DMEPC.352(78) para 4.2 (attained on actual deadweight); MEPC.353(78) Table 1 (bulk carrier 279,000 DWT and above: capacity 279,000 in the reference line); MEPC.354(78) Table 1 (ratio 1.167)Load inputs
Bulk carrier, 82,000 DWT, 2026Required CII: 3.709Shows “Reference line 4.167”MEPC.353(78) Table 1 (a 4745, c 0.622); MEPC.338(76) para 4.1 and Table 1 (Z 11%)Load inputs
Tanker, 115,000 DWT, 2025Required CII: 3.908Shows “Reference line 4.294”MEPC.353(78) Table 1 (a 5247, c 0.610); MEPC.338(76) Table 1 (Z 9%)Load inputs
The other 44 test cases
InputsExpected resultTraced toLoad
Container ship, 150,000 DWT, 2030Required CII: 4.585Shows “Reference line 5.840”MEPC.353(78) Table 1 (a 1984, c 0.489); MEPC.338(76) Table 1 as amended by MEPC.400(83) (Z 21.5%)Load inputs
Bulk carrier, 400,000 DWT (capacity capped at 279,000), 2027Required CII: 1.681Shows “Reference line 1.946”MEPC.353(78) Table 1 (bulk carrier 279,000 DWT and above: capacity 279,000); MEPC.338(76) Table 1 as amended by MEPC.400(83) (Z 13.625%)Load inputs
Gas carrier, 80,000 DWT, 2026Required CII: 8.987Shows “Reference line 10.098”MEPC.353(78) Table 1 (gas carrier 65,000 DWT and above: a 14405E7, c 2.071); MEPC.338(76) Table 1 (Z 11%)Load inputs
General cargo ship, 10,000 DWT, 2025Required CII: 14.942Shows “Reference line 16.420”MEPC.353(78) Table 1 (general cargo ship below 20,000 DWT: a 588, c 0.3885); MEPC.338(76) Table 1 (Z 9%)Load inputs
General cargo ship, 30,000 DWT, 2025Required CII: 8.272Shows “Reference line 9.090”MEPC.353(78) Table 1 (general cargo ship 20,000 DWT and above: a 31948, c 0.792); MEPC.338(76) Table 1 (Z 9%)Load inputs
Combination carrier, 300,000 DWT, 2026Required CII: 1.786Shows “Reference line 2.006”MEPC.353(78) Table 1 (combination carrier: a 5119, c 0.622); MEPC.338(76) Table 1 (Z 11%)Load inputs
LNG carrier, 120,000 DWT, 2026Required CII: 8.746Shows “Reference line 9.827”MEPC.353(78) Table 1 (LNG carrier 100,000 DWT and above: a 9.827, c 0); MEPC.338(76) Table 1 (Z 11%)Load inputs
LNG carrier, 90,000 DWT, 2026Required CII: 7.370Shows “Reference line 8.280”MEPC.353(78) Table 1 (LNG carrier 65,000 to 100,000 DWT: a 14479E10, c 2.673); MEPC.338(76) Table 1 (Z 11%)Load inputs
LNG carrier, 50,000 DWT (capacity fixed at 65,000), 2026Required CII: 17.952Shows “Reference line 20.171”MEPC.353(78) Table 1 (LNG carrier below 65,000 DWT: capacity 65,000, a 14779E10, c 2.673); MEPC.338(76) Table 1 (Z 11%)Load inputs
Vehicle carrier, 60,000 GT (capacity fixed at 57,700), 2026Required CII: 5.010Shows “Reference line 5.629”MEPC.353(78) Table 1 (ro-ro vehicle carrier 57,700 GT and above: capacity 57,700, a 3627, c 0.590); MEPC.338(76) Table 1 (Z 11%)Load inputs
Vehicle carrier, 20,000 GT, 2026Required CII: 11.294Shows “Reference line 12.690”MEPC.353(78) Table 1 (ro-ro vehicle carrier below 30,000 GT: a 330, c 0.329); MEPC.338(76) Table 1 (Z 11%)Load inputs
Ro-ro cargo ship, 30,000 GT, 2026Required CII: 11.798Shows “Reference line 13.256”MEPC.353(78) Table 1 (ro-ro cargo ship: a 1967, c 0.485); MEPC.338(76) Table 1 (Z 11%)Load inputs
Ro-ro passenger ship, 30,000 GT, 2026Required CII: 15.700Shows “Reference line 17.641”MEPC.353(78) Table 1 (ro-ro passenger ship: a 2023, c 0.460); MEPC.338(76) Table 1 (Z 11%)Load inputs
High-speed craft to SOLAS chapter X, 6,000 GT, 2026Required CII: 68.277Shows “Reference line 76.716”MEPC.353(78) Table 1 (ro-ro passenger ship, high-speed craft: a 4196, c 0.460); MEPC.338(76) Table 1 (Z 11%)Load inputs
Tanker, 115,000 DWT, 2025, attained 3.80Required CII: 3.908Attained ÷ required: 0.972Rating: CMEPC.353(78) Table 1 (a 5247, c 0.610); MEPC.338(76) Table 1 (Z 9%); MEPC.354(78) para 4.6 and Table 1 (tanker 0.82 / 0.93 / 1.08 / 1.28)Load inputs
Container ship, 150,000 DWT, 2024, attained 6.80Required CII: 5.431Attained ÷ required: 1.252Rating: EMEPC.353(78) Table 1 (a 1984, c 0.489); MEPC.338(76) Table 1 (Z 7%); MEPC.354(78) Table 1 (container 0.83 / 0.94 / 1.07 / 1.19)Load inputs
Bulk carrier, 400,000 DWT (capacity capped at 279,000), 2026, attained 1.95Required CII: 1.732Attained ÷ required: 1.126Rating: DMEPC.353(78) Table 1 (279,000 DWT and above: capacity 279,000); MEPC.338(76) Table 1 (Z 11%); MEPC.354(78) Table 1 (bulk 0.86 / 0.94 / 1.06 / 1.18)Load inputs
LNG carrier, 80,000 DWT, 2026, attained 12.00Required CII: 10.096Attained ÷ required: 1.189Rating: DMEPC.353(78) Table 1 (LNG carrier 65,000 to 100,000 DWT: a 14479E10, c 2.673); MEPC.338(76) Table 1 (Z 11%); MEPC.354(78) Table 1 (LNG carrier below 100,000 DWT: 0.78 / 0.92 / 1.10 / 1.37)Load inputs
Bulk carrier, 82,000 DWT, 2026, attained 3.95, 6,000 t HFORequired CII: 3.709Attained ÷ required: 1.065Rating: DMEPC.353(78) Table 1 (a 4745, c 0.622); MEPC.338(76) Table 1 (Z 11%); MEPC.354(78) para 4.6 and Table 1 (bulk 0.86 / 0.94 / 1.06 / 1.18); MEPC.352(78) (attained proportional to fuel mass at fixed Cf)Load inputs
Tanker, 115,000 DWT, 2025, attained 3.80, 9,000 t HFORequired CII: 3.908Attained ÷ required: 0.972Rating: CMEPC.353(78) Table 1 (a 5247, c 0.610); MEPC.338(76) Table 1 (Z 9%); MEPC.354(78) Table 1 (tanker 0.82 / 0.93 / 1.08 / 1.28)Load inputs
Bulk carrier, 400,000 DWT (capacity capped at 279,000), 2026, attained 1.95, 25,000 t HFORequired CII: 1.732Attained ÷ required: 1.126Rating: DMEPC.353(78) Table 1 (279,000 DWT and above: capacity 279,000); MEPC.338(76) Table 1 (Z 11%); MEPC.354(78) Table 1 (bulk d3 1.06, d4 1.18)Load inputs
Attained CII 4.40 in 2024 and 4.30 in 2025, bulk carrier of 82,000 DWTChange in attained CII: -2.3Change in required CII: -2.2Change (4.30 / 4.40 − 1) = −2.27%; required changes by (1 − 0.09) / (1 − 0.07) − 1 = −2.15% under MEPC.338(76)Load inputs
Bulk carrier, 82,000 DWT, 60,000 nm, 5,600 t HFO, 2026Attained CII: 3.544Required CII: 3.709Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Bulk carrier (VLOC), 400,000 DWT, reference line at the 279,000 DWT cap, 52,000 nm, 13,500 t HFO, 2026Attained CII: 2.021Required CII: 1.732Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Gas carrier, 80,000 DWT, 70,000 nm, 14,000 t HFO, 400 t MDO/MGO, 2026Attained CII: 8.014Required CII: 8.987Rating: BCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Gas carrier, 40,000 DWT, 60,000 nm, 7,000 t HFO, 300 t MDO/MGO, 2026Attained CII: 9.483Required CII: 8.267Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Tanker, 115,000 DWT, 55,000 nm, 8,500 t HFO, 500 t MDO/MGO, 2026Attained CII: 4.438Required CII: 3.822Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Container ship, 150,000 DWT, 90,000 nm, 21,000 t HFO, 1,500 t MDO/MGO, 2026Attained CII: 5.200Required CII: 5.198Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
General cargo ship, 30,000 DWT, 45,000 nm, 3,600 t HFO, 300 t MDO/MGO, 2026Attained CII: 9.016Required CII: 8.090Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
General cargo ship, 8,000 DWT, 30,000 nm, 1,220 t MDO/MGO, 2026Attained CII: 16.297Required CII: 15.937Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Refrigerated cargo carrier, 12,000 DWT, 55,000 nm, 4,000 t HFO, 400 t MDO/MGO, 2026Attained CII: 20.816Required CII: 21.880Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Combination carrier, 300,000 DWT, 50,000 nm, 9,500 t HFO, 2026Attained CII: 1.972Required CII: 1.786Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
LNG carrier, 120,000 DWT, 80,000 nm, 28,000 t LNG, 1,000 t MDO/MGO, 2026Attained CII: 8.355Required CII: 8.746Rating: BCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
LNG carrier, 90,000 DWT, 75,000 nm, 17,000 t LNG, 800 t MDO/MGO, 2026Attained CII: 7.306Required CII: 7.370Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
LNG carrier, 50,000 DWT, reference line at 65,000 DWT, 60,000 nm, 19,900 t LNG, 600 t MDO/MGO, 2026Attained CII: 18.883Required CII: 17.952Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro vehicle carrier, 60,000 GT, reference line at 57,700 GT, 70,000 nm, 6,450 t HFO, 500 t MDO/MGO, 2026Attained CII: 5.164Required CII: 5.010Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro vehicle carrier, 45,000 GT, 65,000 nm, 4,660 t HFO, 400 t MDO/MGO, 2026Attained CII: 5.400Required CII: 5.802Rating: BCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro vehicle carrier, 20,000 GT, 60,000 nm, 4,480 t HFO, 300 t MDO/MGO, 2026Attained CII: 12.427Required CII: 11.294Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro cargo ship, 30,000 GT, 70,000 nm, 8,000 t HFO, 500 t MDO/MGO, 2026Attained CII: 12.626Required CII: 11.798Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro passenger ship, 30,000 GT, 90,000 nm, 14,000 t HFO, 1,000 t MDO/MGO, 2026Attained CII: 17.334Required CII: 15.700Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Ro-ro passenger high-speed craft, 6,000 GT, 60,000 nm, 8,000 t MDO/MGO, 2026Attained CII: 71.244Required CII: 68.277Rating: CCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs
Cruise passenger ship, 100,000 GT, 55,000 nm, 16,300 t HFO, 3,000 t MDO/MGO, 2026Attained CII: 10.977Required CII: 10.066Rating: DCf MEPC.364(79); attained MEPC.352(78) as amended by MEPC.412(84); reference line MEPC.353(78) Table 1; Z 11% MEPC.338(76); boundaries MEPC.354(78) Table 1Load inputs

Change log

Each change to the method, a coefficient or a test case, with the date it reached this page.

  • Rebuilt with drawings and sliders: the ship type as cards, each with its silhouette and the capacity it is rated on; a slider beside every number box, the capacity marked at the MEPC.353(78) size rows and the 2023 fleet mean from MEPC 82/6/38; the year as chips showing Z; and the result drawn as the A to E bands with the ship’s ratio, the bands for every year to 2030, the headroom to each band edge and the reference line with the ship on it. The distance wording now cites MEPC.401(83) and MEPC.413(84), the fixed-capacity edge case cites IACS Recommendation 175, and the VLSFO factor follows its ISO 8217 grade. The arithmetic and the 49 test cases are unchanged.
  • Merged the attained, required, rating, attained-versus-required and year-on-year calculators into this page. Gas carriers now take their MEPC.353(78) row and MEPC.354(78) boundaries from the deadweight entered, and the distance counts miles traveled both under way and not under way, under MEPC.412(84).
  • Reference lines moved to MEPC.353(78) Table 1 with its size bands; the earlier data carried the revoked MEPC.337(76) values.

Who publishes this calculator and how it is checked

Publisher
ShipCalculators.com, an independent site of maritime calculators.
How it is checked
Each figure is traced to the instrument that sets it, and the test cases on this page run against the calculator code on every build; a build that moves one of them does not deploy. Last method check: 18 October 2026.
What it is not
Not the rating of record, and not endorsed by any flag Administration or classification society. The rating that counts is the one in the ship's Statement of Compliance.

Calculators used with this one

A ship rated D for three years running, or E once, needs a corrective action plan; the CII corrective-plan projector works out the cut it needs and the year the rating recovers.

The same fuel burned in EU trade also carries an EU ETS allowance cost, which the EU ETS EUA liability calculator prices, and a FuelEU Maritime intensity limit, which the FuelEU GHG intensity calculator checks.

Regulation and sources

  1. IMO MEPC.328(76): 2021 revised MARPOL Annex VI, Regulation 28
  2. IMO MEPC.352(78): 2022 CII Guidelines (G1)
  3. IMO MEPC.412(84): amendments to the CII Guidelines (G1), section 4.2
  4. IMO MEPC.353(78): 2022 CII Reference Lines Guidelines (G2), Table 1
  5. IMO MEPC.338(76): 2021 CII Reduction Factors Guidelines (G3)
  6. IMO MEPC.400(83): reduction factors for 2027 to 2030
  7. IMO MEPC.354(78): 2022 CII Rating Guidelines (G4), Table 1
  8. IMO MEPC.364(79): 2022 EEDI calculation guidelines, Cf in para 2.2.1
  9. IMO MEPC.355(78): interim guidelines on correction factors and voyage adjustments (G5)
  10. IMO MEPC.401(83): amendments to the SEEMP Guidelines, para 7.6 under way and not under way
  11. IMO MEPC.413(84): amendments to the SEEMP Guidelines, para 7.7.2 distance
  12. IMO MEPC 82/6/38: report of fuel oil consumption data for 2023, Tables 2 and 3