CBM Calculator: Sea Freight Volume & Chargeable Weight

Formula, assumptions, and limits

To calculate CBM, multiply a package’s length, width, and height in meters, then multiply by the number of packages:

$$V_{\text{CBM}} = L \cdot W \cdot H \cdot n$$

L, W, H - package length, width, and height converted to meters (1 cm = 0.01 m, 1 in = 0.0254 m). n - number of identical packages.

Sea LCL is billed per revenue ton on the weight-or-measurement basis:

$$RT = \max\left(V_{\text{CBM}},; \frac{m_{\text{gross}}}{1000,\text{kg}}\right)$$

so 1 revenue ton is 1 cubic meter or 1,000 kg of gross weight, whichever produces the larger figure. Volumetric (dimensional) weight for the other modes divides the volume in cubic centimeters by the mode’s divisor: 6,000 cm³/kg for air freight under IATA practice (equivalent to 167 kg per CBM), 5,000 cm³/kg for most express couriers (200 kg per CBM), and about 3,000 cm³/kg for European road groupage (333 kg per CBM). The mode bills the greater of actual gross weight and volumetric weight.

Worked example: 250 cartons of 60 × 40 × 40 cm at 12 kg each. One carton is 0.096 m³, so the consignment is 24.0 CBM and 3,000 kg. Sea LCL charges on measurement: 24.0 revenue tons. Air freight converts 24.0 CBM at 6,000 cm³/kg to 4,000 kg volumetric, which exceeds the 3,000 kg actual weight, so the air chargeable weight is 4,000 kg. The shipment fills 72% of a 20’ GP container by volume at 11% of its payload, so volume governs and one 20’ GP carries it.

The container-fit figures use typical internal volumes and maximum payloads for ISO 668 series 1 general-purpose boxes: 33.2 m³ and about 28,180 kg for the 20’ GP (1CC), 67.7 m³ and about 26,700 kg for the 40’ GP (1AA), 76.4 m³ and about 26,460 kg for the 40’ high cube (1AAA). ISO 668 fixes external dimensions and gross ratings; internal volume and payload vary by manufacturer and tare, so treat the fit as an estimate and verify against the specific unit’s CSC plate. Practical stuffing of regular cartons reaches 80 to 90% of internal volume; irregular or non-stackable cargo achieves less. The calculator assumes identical rectangular packages and does not model carton orientation, pallet overhang, or mixed-size loads. Courier divisors differ by carrier and service (5,000 cm³/kg is common but not universal); check the carrier’s current terms for a binding quote.

How to use this calculator

1. Measure one package’s length, width, and height at the longest points, packaging included. For palletized cargo, measure the loaded pallet: carriers charge on the pallet footprint and height, not the cartons inside it.
2. Select the measurement unit (cm, m, mm, or in); the calculator converts to meters internally.
3. Enter the three dimensions and the number of identical packages.
4. Enter the gross weight per package in kilograms, from the packing list or a scale.
5. Read the total CBM, the sea LCL revenue tons on the W/M basis, the air, courier, and road chargeable weights, and the container-fit strip for 20-foot and 40-foot equipment.

For mixed-size consignments, run each size separately and add the CBM figures; the W/M comparison applies to the consignment total.

Volumetric divisors and break-even densities

The break-even density is the decision tool: cargo denser than the mode’s figure pays on actual weight, cargo lighter pays on volume. Flat-packed furniture at 120 kg/m³ is volumetric on every mode; machine parts at 800 kg/m³ are volumetric only on sea LCL; steel fittings at 2,000 kg/m³ pay actual weight everywhere, and on sea LCL the weight side of the W/M comparison governs. European road groupage also prices long, low cargo per loading metre (1 ldm is conventionally 1,750 kg), which a volumetric divisor does not capture; quote both ways for trailer cargo.

Quick conversions

1 CBM = 35.31 ft³ = 1,000 liters. The US measurement ton (the freight ton the W/M revenue ton descends from) is 40 ft³ = 1.133 m³. 1 ft³ = 0.0283 m³; 1 in = 2.54 cm exactly. Internal container dimensions are governed by ISO 1496 test requirements rather than ISO 668, which fixes external dimensions and gross ratings; that is why internal volume varies by manufacturer while external sizes never do.

Common errors

1. Unit mix-up. Entering centimeter measurements with the meter unit selected inflates volume by a factor of one million. A 60 cm carton entered as 60 m is the single most common cause of absurd CBM figures.
2. Inner instead of outer dimensions. Carriers measure the outermost points, including packaging, strapping, and pallet overhang. Catalogue product dimensions understate freight dimensions.
3. Ignoring the pallet. A 1.2 × 1.0 m pallet at 15 cm height adds 0.18 m³ before any cargo, and palletized freight is measured at the loaded pallet envelope, not as loose cartons.
4. Wrong divisor for the service. Quoting a courier shipment at the IATA 6,000 factor produces a volumetric weight 17% below the figure the courier bills on its 5,000 factor; the invoice comes back 20% above the quote.
5. Forgetting the weight side of W/M. Dense cargo can exceed 1 t/m³; pricing 18 t of fittings in 9 m³ as 9 revenue tons halves the real LCL charge of 18 RT.

When to use this calculator

Use this tool when you have package dimensions and need volume, chargeable weight, or equipment fit. If you already hold a carrier quote and want to verify the billed figure, the chargeable weight calculator prices a single mode with carrier-specific divisors: the quote’s volumetric divisor should be stated on the rate sheet. For full-container pricing the CBM figure matters only for the fit check; FCL is priced per box, not per cubic meter, which is why consolidations above roughly 15 CBM deserve an FCL comparison quote, and the FCL vs LCL break-even calculator computes the exact crossing for your lane before you book LCL.

About This CBM Calculator

CBM, the cubic meter, is the volume unit ocean freight is measured and billed in. This CBM calculator is for shippers, freight forwarders, and export managers who need the volume of a consignment in cubic meters and the chargeable weight the carrier bills. It takes the dimensions of one package in centimeters, meters, millimeters, or inches, the package count, and the gross weight per package, and returns the total CBM, the total gross weight, the sea LCL revenue tons on the weight-or-measurement basis, and the air chargeable weight.

The volume arithmetic is the universal freight convention: length times width times height converted to meters, times the number of packages. Sea LCL pricing follows the W/M revenue-ton rule (1 m³ or 1,000 kg, whichever is greater) used across NVOCC and consolidator tariffs. The volumetric conversions follow IATA practice for air cargo at 6,000 cm³ per kg, the common express-courier divisor of 5,000 cm³ per kg, and the road-groupage convention of about 3,000 cm³ per kg. Container-fit checks use ISO 668 series 1 designations with typical internal volumes and payloads for the 20’ GP, 40’ GP, and 40’ high cube.

The chart makes the billing logic visible: for each mode it draws the actual weight beside the mode’s volumetric weight, so you can see at a glance which side of the W/M comparison your cargo falls on and how far.

A dense machinery shipment shows actual weight towering over every volumetric bar; a light furniture load shows the opposite. The container-fit strip below reports volume and payload utilization separately and names which one governs, which is the difference between booking LCL and booking a full box.

Further reading

• CBM (cubic meter) in freight
• Chargeable weight
• Container ship
• Chargeable weight calculator
• FCL vs LCL break-even calculator

Frequently asked questions

What is CBM in shipping?

CBM stands for cubic meter, the volume unit ocean freight is measured and billed in. One CBM is the volume of a cube one meter on each side. Total CBM is length times width times height of one package, in meters, multiplied by the number of packages.

How do you calculate CBM?

Multiply a package's length, width, and height in meters, then multiply by the number of packages. A 60 x 40 x 40 cm carton is 0.6 x 0.4 x 0.4 = 0.096 CBM, so 250 such cartons total 24 CBM. Dimensions in centimeters divide by 100 first; inches multiply by 0.0254.

How many kg is 1 CBM?

It depends on the mode's volumetric convention: sea LCL equates 1 CBM to 1,000 kg (the W/M revenue-ton rule), air freight to about 167 kg (the IATA 6,000 cm3/kg divisor), couriers to 200 kg (5,000 cm3/kg), and road groupage to about 333 kg (3,000 cm3/kg).

How is sea LCL freight charged per CBM?

LCL (less-than-container-load) freight is billed per revenue ton on a weight-or-measurement (W/M) basis: one revenue ton equals 1 cubic meter or 1,000 kg, whichever yields the greater figure. Light, bulky cargo pays on volume; dense cargo pays on weight.

What is the difference between CBM and chargeable weight?

CBM is the physical volume. Chargeable weight is the billing figure after applying a mode's volumetric divisor: air freight converts at 6,000 cm3 per kg (167 kg per CBM) under IATA practice, couriers commonly at 5,000 cm3 per kg (200 kg per CBM), road groupage at about 3,000 cm3 per kg (333 kg per CBM). The carrier bills the greater of actual and volumetric weight.

How many CBM fit in a 20-foot or 40-foot container?

Typical internal volumes are about 33.2 CBM for a 20' GP, 67.7 CBM for a 40' GP, and 76.4 CBM for a 40' high cube. Practical stuffing with regular cartons reaches 80 to 90% of those figures, and the container's maximum payload can govern before volume does for dense cargo.