CBM stands for cubic metre, the standard volume unit for ocean, air, and road freight. Freight forwarders quote and invoice on CBM because most general cargo cubes out (fills the space) before it weighs out (hits the weight limit).

How is CBM calculated?

Convert each dimension to metres, multiply length by width by height for one box, then multiply by the number of boxes. A carton 60 by 40 by 30 cm is 0.072 CBM, so 100 of them total 7.2 CBM.

What is volumetric weight for air freight?

Air freight uses a 1:6000 ratio, where one cubic metre equals 167 kilograms of chargeable weight. The airline bills the greater of actual weight and this volumetric weight, so bulky light cargo pays on volume.

How much CBM fits in a container?

A 20ft container holds roughly 33 CBM of usable space and a 40ft holds about 67 CBM, with a 40ft high cube around 76 CBM. Real loads reach 80 to 90 percent of these figures once packing gaps are accounted for.

Should I ship by sea or air?

Compare cost per CBM. Sea freight is far cheaper per CBM but slower; air is priced on the higher of weight or volumetric weight and suits dense, urgent, or high-value cargo. This tool gives both the CBM and the air volumetric weight to compare.

CBM (Cubic Metre) Cargo Calculator

CBM — cubic metres — is the unit freight forwarders book and bill on, because most cargo runs out of space before it runs out of weight allowance. This calculator turns your carton dimensions and quantity into total CBM, then shows how that volume maps to containers and to air-freight chargeable weight.

How it works

Each dimension is converted to metres and multiplied, then scaled by quantity:

per-box CBM = (L × W × H, all in metres)
total CBM   = per-box CBM × number of boxes
air volumetric weight (kg) = total CBM × 167   (1:6000 rule)

The total CBM is then compared against usable container capacities — about 33 CBM for a 20ft, 67 CBM for a 40ft, and 76 CBM for a 40ft high cube — to estimate fill percentage.

Example and tips

A carton measuring 60 by 40 by 30 cm is 0.072 CBM. A hundred of them total 7.2 CBM, which fills roughly 22 percent of a 20ft container and gives an air-freight volumetric weight of about 1200 kg. If the actual weight is below that, the airline still charges on 1200 kg. When a shipment cubes out well before the container’s weight limit, consolidating into denser packaging or upgrading to a 40ft box is usually the cheaper move per unit shipped.