How weight and volume affect shipping costs
Is sea freight charged by cubic metre or by tonne? How is air volumetric weight calculated? Formulas and examples for working out chargeable weight.
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Sea LCL is usually compared at "1 cubic metre to 1,000 kg", charging whichever is greater. Air freight uses "length × width × height (cm) ÷ 6,000" to get the volumetric weight, compared with the actual weight, charging whichever is greater.
Information updated: 2026-10-03
Sea freight: calculating cubic metres
- Measure one carton's length, width and height (in metres) and multiply them to get the volume of one carton.
- Multiply by the number of cartons to get the total cubic metres.
- Compare with the total weight in tonnes: if tonnes exceed cubic metres, it's heavy cargo charged by weight; otherwise it's bulky cargo charged by volume.
| Example | Calculation | Result |
|---|---|---|
| 100 cartons of 60 × 40 × 50 cm | 0.6 × 0.4 × 0.5 × 100 | 12 m³ |
| Same shipment weighs 3 tonnes in total | 3 tonnes < 12 m³ | Charged as 12 m³ (bulky cargo) |
| Replace with 12 tonnes of hardware | 12 tonnes ≥ 12 m³ | Charged by weight (heavy cargo) |
Air freight: calculating volumetric weight
The usual air volumetric factor is 6,000: length × width × height (cm) ÷ 6,000 = volumetric weight (kg). Express channels often use 5,000; the smaller the factor, the larger the volumetric weight.
For example, a 60 × 50 × 40 cm carton weighing 15 kg has a volumetric weight of 20 kg, so it is charged as 20 kg.
How to reduce the chargeable amount
- Compress packaging: clothing and soft goods can be vacuum-packed to cut cubic metres.
- Choose cartons sensibly: oversized cartons with empty space mean paying to ship air.
- Load heavy and bulky goods together so both the weight and volume of the container are used.
Give accurate carton sizes and gross weights when asking for a quote. Large estimation errors are settled at the warehouse's measured figures in the end.