CBM, or cubic metre, is the standard unit of volume in international shipping. Freight forwarders ask for total CBM to quote sea freight, plan containers and calculate warehouse charges. This guide shows how to calculate CBM from cm, mm or inches, with our free CBM Calculator.
The basic formula
CBM = Length × Width × Height (all in metres)
From centimetres
CBM = L × W × H (cm) ÷ 1,000,000
Example: 50 × 40 × 30 cm = 60,000 cm³ = 0.06 CBM.
From millimetres
CBM = L × W × H (mm) ÷ 1,000,000,000
Example: 500 × 400 × 300 mm = 0.06 CBM.
From inches
CBM = L × W × H (in) ÷ 61,024
Example: 20 × 16 × 12 in = 3,840 in³ ÷ 61,024 = 0.063 CBM.
Total shipment CBM
Multiply CBM per carton by the number of cartons. For mixed sizes, calculate each line and add them up.
| Cartons | Size (cm) | CBM each | Total |
|---|---|---|---|
| 100 | 50 × 40 × 30 | 0.060 | 6.00 |
| 60 | 45 × 35 × 25 | 0.039 | 2.36 |
| Total | 8.36 |
CBM and cubic feet
1 CBM = 35.315 cubic feet.
Common mistakes
- Mixing cm and mm
- Using inner box dimensions instead of outer
- Forgetting pallets, which add volume (a 1.2 × 1.0 m pallet with load 1.5 m high is 1.8 CBM)
Why CBM matters
- Sea freight LCL is charged per CBM or per tonne.
- Containers are planned by CBM; see the Container Volume Calculator.
- Chargeable weight in air freight relates to CBM; see the CBM to KG Calculator.
For LCL charges, read CBM and LCL shipping charges. For carton totals, see carton volume in CBM.
Measuring cartons correctly
Measure the outside of the packed, sealed carton with a steel tape. Bulging cartons should be measured at their widest point. Round each dimension up to the next whole centimetre, as forwarders and warehouses usually do. Measure several cartons from a batch, since sizes can vary slightly.
Frequently asked questions
How do I calculate CBM from cm?
Multiply length, width and height in cm and divide by 1,000,000.
How many cubic feet are in 1 CBM?
About 35.315 cubic feet.
Should I use inner or outer carton dimensions?
Outer dimensions.