FuelEU Maritime GHG Intensity Calculator: Mix vs Target

Formula, assumptions, and limits

The attained intensity under Regulation (EU) 2023/1805 is the energy-weighted well-to-wake emission rate of everything the ship burned. To calculate it, weight each fuel’s factor by its energy and divide by the (multiplier-adjusted) energy total:

M_j - mass of fuel j burned in the year, tonnes. LCV_j - its lower calorific value, MJ/kg. WtW_j - its well-to-wake factor, gCO₂e/MJ, per Annex II defaults or certified actuals. m_j - the multiplier: 2 for renewable fuels of non-biological origin from 2025 through 2033, 1 otherwise.

The target it compares against starts at 89.34 gCO₂e/MJ (2 percent under the 91.16 baseline) for 2025-2029, steps to 6 percent under in 2030, and reaches 80 percent under by 2050. The trajectory is the regulation’s core design: every mix that complies today has a year on the chart where it stops, and fleet fuel strategy is the business of moving that year out past the ships’ lives.

Assumptions and limits: the calculator uses Annex II default factors through the shared fuel library; suppliers’ certified actual values can lawfully beat the defaults upstream of the funnel and would lower the attained figure. Wind-assist reward factors, the OPS (shore power) zero-rating at berth, and the small premium the regulation puts on specific fuel pathways are not modeled row by row; they adjust the inputs rather than the formula. Scope mirrors the EU ETS geography (100 percent intra-EEA energy, 50 percent in/out), so the energy entered should already be the scoped figure.

How to use this calculator

1. Select the compliance year for the target.
2. Add a row per fuel and enter the tonnes burned.
3. Read the attained intensity, the target, and the gap.
4. On the trajectory chart, find where the flat mix line crosses the stepped target line: that is the year this mix stops complying.

Worked example

A mix of 2,000 t VLSFO and 500 t of B100 biodiesel. The biodiesel’s low well-to-wake factor pulls the energy-weighted average well under the fossil baseline, and against the 2025-2029 target of 89.34 the mix attains a comfortable surplus; the chart shows the same mix clearing the 2030 step and failing at the 2035 one (77.94), which is the regulation working as designed: a 20 percent biofuel blend buys a decade, not a pass. Swap the biodiesel for more VLSFO and the mix sits near 91 gCO₂e/MJ: over target from day one, accruing a deficit the compliance balance calculator turns into euros.

Reading the trajectory like a fleet planner

The staircase is the strategy document. A conventional VLSFO ship fails from 2025; a modest biofuel blend clears the first step and fails at 2030; LNG tonnage with managed slip typically clears 2030 and meets its wall at the 2035 step; only fuels with deep well-to-wake cuts survive the 2040 tightening. Because the steps are five-yearly and known, the planning question is never whether a mix complies now but which step kills it, and whether that year falls inside the ship’s remaining life or a charter’s tail. Fleets hedge across the staircase: surplus ships built early (the RFNBO double count helps) bank and pool against the laggards, which converts the trajectory from a per-ship cliff into a portfolio glide. The chart on this page draws exactly that conversation for one mix.

Common errors

1. Tank-to-wake thinking. FuelEU is well-to-wake: a fuel that burns clean but is made dirty fails on its production chain, and grey methanol or ammonia can attain worse than the diesel it replaced.
2. Forgetting methane slip. The WtW factors carry CH₄ and N₂O; LNG’s combustion slip is in its number, which is why engine technology differentiates LNG fuels in Annex II.
3. Misapplying the RFNBO multiplier. The 2x rides only on renewable fuels of non-biological origin, only through 2033, and only in the energy denominator; biofuels do not get it.
4. Comparing unscoped energy. The intensity is computed on the FuelEU-scoped energy (intra-EEA full, in/out half); feeding global consumption in overstates both energy and the balance built on it.

About This FuelEU GHG Intensity Calculator

Where the EU ETS counts tonnes, FuelEU Maritime grades megajoules: the well-to-wake intensity of a ship’s energy must beat a target that tightens every five years. Built for operators, fuel buyers, and compliance teams working an actual or planned fuel mix, this page takes tonnes per fuel from the shared marine-fuel library’s Annex II-aligned factors and returns the attained figure, the year’s target, and the gap.

The arithmetic is Annex I’s: energy-weighted well-to-wake intensity with the RFNBO double-count in the denominator through 2033. The 2025-2029 target of 89.34 gCO₂e/MJ is two percent under the 91.16 baseline, and the page treats the trajectory, not the current step, as the real object: the chart overlays your mix on the full staircase to 2050 so the non-compliance year is a visible fact rather than a projection exercise.

The library behind the rows is the same one the site’s CII and ETS calculators draw on, so the three regimes price one fuel ledger consistently instead of three contradictory ones. Downstream of this page, the gap becomes money: the compliance balance calculator turns attained-versus-target into the balance, the VLSFO-equivalent, and the EUR 2,400 penalty, with banking, borrowing, and pooling as the remedies in between. The ETS twin lives in the EUA liability calculator: same voyages, the other bill.

Further reading

• FuelEU Maritime explained
• FuelEU penalties, pooling, and the RFNBO multiplier
• Well-to-wake intensity
• FuelEU compliance balance calculator
• EU ETS EUA liability calculator

Frequently asked questions

What is FuelEU Maritime?

Regulation (EU) 2023/1805, applying since 1 January 2025: ships above 5,000 GT trading in the EEA must keep the well-to-wake greenhouse-gas intensity of their energy use below a target that declines from 2 percent under the 2020 fleet baseline (91.16 gCO₂e/MJ) to 80 percent under it by 2050.

How is the attained GHG intensity calculated?

Energy-weighted: each fuel's mass times its lower calorific value gives its energy, each energy times its well-to-wake emission factor gives its emissions, and total emissions over total energy is the attained intensity in gCO₂e/MJ. Renewable fuels of non-biological origin count their energy twice in the denominator through 2033, a reward for early uptake.

What counts as well-to-wake?

The whole fuel chain: extraction or production, processing, transport, and the onboard combustion including methane and nitrous oxide, not just the CO₂ leaving the funnel. Annex II of the regulation carries the default factors, and certified actual values can replace them upstream.

What is the difference between the EU ETS and FuelEU Maritime?

The ETS prices the quantity of greenhouse gas a ship emits: every scoped tonne needs an allowance. FuelEU regulates the quality of the energy: the well-to-wake intensity per megajoule must beat a declining target regardless of how much is burned. The same voyage pays both, and the same fuel choice moves both bills.

What happens if the attained intensity is above the target?

The gap times the energy used becomes a negative compliance balance, which the ship can cover by banking from earlier surpluses, borrowing from the next year within limits, or pooling with surplus ships; whatever remains is penalized at EUR 2,400 per tonne of VLSFO-equivalent energy. The compliance balance calculator prices it.