Reviewed November 2026. Formulas are shown above the guide. Report an error or request a calculator.
Why CBM drives the sea freight bill
Ocean freight is sold by space. A full container (FCL) has a fixed price whatever you put in it, while less-than-container (LCL) cargo is billed per cubic metre or per tonne, whichever is larger. Knowing the cubic metres of a shipment before you book tells you which container to ask for, whether LCL or FCL is cheaper, and how many cartons you can add to fill the space you are already paying for.
Worked example
250 cartons of 60 × 40 × 40 cm weighing 18 kg each:
| Item | Value |
|---|---|
| CBM per carton (0.6 × 0.4 × 0.4) | 0.096 m³ |
| Total volume | 24.00 m³ |
| Total weight | 4,500 kg |
| 20ft fill (28 m³ loadable) | 86% |
| Cartons that would fit by volume | about 291 |
| LCL charge basis | 24.00 revenue tons |
The load fits one 20ft container with room for about 40 more cartons. At 24 m³ a full 20ft is almost always cheaper than paying LCL rates on 24 revenue tons.
LCL or FCL?
LCL is billed per revenue ton: the larger of the volume in cubic metres and the weight in tonnes. It also carries consolidation and terminal fees on both ends. As a rule of thumb, once a shipment passes 13–15 m³ a 20ft container usually costs the same or less, and it is handled less, which means less damage. Ask for both quotes around that size.
Common mistakes
- Planning to the internal volume. A 20ft has about 33 m³ inside, but real loads rarely exceed 25–28 m³.
- Ignoring weight limits. Dense goods such as tiles or metal parts hit the payload limit, or national road limits, long before the container is full.
- Forgetting pallets. Palletised cargo loses 10–20% of the usable space.
Frequently asked questions
How do I calculate CBM?
Multiply length × width × height in metres for one carton, then multiply by the number of cartons. In centimetres, divide the product by 1,000,000.
How many CBM fit in a 20ft container?
About 33 m³ inside, and about 25–28 m³ of cartons in practice.
How many CBM fit in a 40ft high-cube?
About 76 m³ inside and roughly 65–68 m³ of cartons in practice.
What is a revenue ton?
The LCL billing unit: the greater of the cargo volume in cubic metres and its weight in metric tonnes.