CBM calculator
Cubic metres from carton dimensions in any unit, converted to cubic feet, with the air chargeable weight and the ocean LCL revenue ton worked out alongside.
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How the units line up
| CBM | Cubic feet | Air volumetric kg | Ocean R/T |
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What CBM is
One cubic metre is 35.31 cubic feet, or 61,024 cubic inches. A carton 100 by 80 by 60 cm is 0.48 CBM, and twenty of them are 9.6 CBM, which is most of a 20-foot container's usable 28 or so.
Air freight: 1 CBM is 166.67 kg
Air charges on the greater of gross weight and volumetric weight, and volumetric weight comes from the IATA divisor of 6,000 cubic centimetres per kilogram. A cubic metre is 1,000,000 cm³, so it counts as 166.67 kg however little it actually weighs.
That gives a break-even density of about 167 kg per cubic metre. Denser than that and you pay on the scale; lighter and you pay for the space. Most retail goods are lighter, which is why air freight quotes so often come back higher than the shipper expected.
Ocean LCL: the revenue ton
Less-than-container-load ocean freight charges on the revenue ton, also written R/T or W/M for weight or measure. It is the greater of the shipment's cubic metres and its weight in metric tons, counting one cubic metre as one tonne.
So the ocean break-even is 1,000 kg per cubic metre — the density of water. Almost nothing is denser than water once it is packed, so LCL shipments are nearly always charged on volume. Reducing cube is what reduces the bill.
The two modes disagree, and that matters
Air counts a cubic metre as 167 kg; ocean counts it as 1,000 kg. The same carton can be billed on weight by air and on volume by sea. When you are comparing quotes, compare the chargeable figures rather than the rate per kilo, because they are not measuring the same thing.
Questions
How do you calculate CBM?
Multiply length by width by height, all in metres. For centimetres, multiply the three and divide by 1,000,000. A carton 100 by 80 by 60 cm is 0.48 CBM. Multiply by the number of cartons for the shipment total.
How many cubic feet is 1 CBM?
35.31 cubic feet. Going the other way, one cubic foot is 0.0283 CBM. The conversion comes from a foot being exactly 0.3048 metres, so a cubic foot is 0.3048 cubed.
How many kg is 1 CBM in air freight?
166.67 kg, from the IATA divisor of 6,000 cm³ per kilogram. If your shipment is lighter than 166.67 kg per cubic metre, air freight charges you on volume rather than on the scale.
What is chargeable weight?
The figure the freight is actually billed on. For air it is the greater of gross weight and volumetric weight at 6,000 cm³/kg. For ocean LCL it is the revenue ton, the greater of cubic metres and metric tons.
What is a revenue ton in LCL shipping?
The greater of the shipment's volume in cubic metres and its weight in metric tons, sometimes written W/M. Since one cubic metre has to weigh a full tonne to be charged by weight, and water is exactly that dense, LCL is nearly always charged on volume.
How many CBM fit in a 20ft container?
A 20-foot container has about 33 CBM of internal volume, but 25 to 28 is realistic once pallets, packing and the fact that boxes do not tessellate perfectly are accounted for. A 40-foot container runs about 55 to 60 CBM in practice.