GUIDE · RATES
What volumetric weight is and how it is calculated
Volumetric weight is a notional weight for a shipment calculated from its dimensions rather than from the scales. The carrier charges on the greater of two values: actual weight or volumetric weight. The reason is that space in a container and on an aircraft is limited by volume just as much as by tonnage: 40 kg of cushions will take up several cubic metres, and nobody can move them at the price of 40 kg. The formula is the same for every mode of transport — length × width × height — what differs is the divisor: in air freight it is 6000 (1 m³ ≈ 167 kg), in consolidated sea freight 1 m³ is treated as 1000 kg, and rail and road use intermediate ratios.
Why volumetric weight is calculated at all
Imagine two consignments of 500 kg each. The first is auto parts in one cubic metre. The second is inflatable mattresses in five cubic metres. On the scales they are identical. In a container the second takes up five times more space, and a container is sold precisely by the cubic metre.
Volumetric weight evens out this unfairness. It converts volume into kilograms at a fixed rate, and you then pay whichever of the two is greater. It is not a way of charging more — it is a way of pricing dense and light goods on the same basis.
The formula and the divisors by mode of transport
The basic formula for air and express:
Volumetric weight (kg) = length × width × height in cm ÷ divisor
For sea, rail and road it is more convenient to work from the volume in cubic metres and the ratio of "how many kilograms in one cubic metre".
| Mode of delivery | Divisor / ratio | 1 m³ equals | Threshold density |
|---|---|---|---|
| Air (IATA standard) | 6000 | ≈ 167 kg | 167 kg/m³ |
| Express couriers | 5000 | 200 kg | 200 kg/m³ |
| Sea, consolidated cargo (LCL) | 1 m³ = 1000 kg | 1000 kg | 1000 kg/m³ |
| Rail, consolidated cargo | usually 1 m³ = 300–500 kg | 300–500 kg | 300–500 kg/m³ |
| Road, consolidated cargo | usually 1 m³ = 250–333 kg | 250–333 kg | 250–333 kg/m³ |
| Sea, container (FCL) | not applicable, rate per container | — | — |
The threshold density in the right-hand column is the most useful number in this table. If the density of your cargo is above it, you pay for actual weight. If it is below, you pay for volumetric weight — that is, effectively for the air inside your boxes.
Example: one consignment, three modes of transport
Consignment: 20 boxes of 60 × 40 × 40 cm, total weight 200 kg.
- Volume of one box: 60 × 40 × 40 = 96,000 cm³ = 0.096 m³.
- Volume of the consignment: 0.096 × 20 = 1.92 m³.
- Density: 200 ÷ 1.92 = 104 kg/m³. This is light cargo.
| Mode | Volumetric weight calculation | Which is greater | Chargeable |
|---|---|---|---|
| Air | 1,920,000 cm³ ÷ 6000 = 320 kg | volumetric | 320 kg |
| Rail (1 m³ = 500 kg) | 1.92 × 500 = 960 kg | volumetric | 960 kg |
| Sea LCL (1 m³ = 1000 kg) | 1.92 × 1000 = 1920 kg | volumetric | 1.92 m³ |
Note the sea row: when volume is the chargeable basis, the rate is usually not converted into kilograms but simply charged by the cubic metre. Formally it is the same operation — the "freight tonne", the greater of weight and volume.
A second example: why the same weight costs different amounts
Two consignments of 500 kg each fly by air at an indicative rate of $5 per kg.
Consignment A: spare parts, 1 m³. Volumetric weight 167 kg, actual weight 500 kg. Chargeable 500 kg → $2500.
Consignment B: plastic containers, 5 m³. Volumetric weight 5 × 167 = 835 kg, actual weight 500 kg. Chargeable 835 kg → $4175.
The same weight, a difference in price of two thirds. The whole difference is in packing and density.
How not to pay for air
- Calculate per package, not for the consignment as a whole. The carrier measures each box separately and adds the results. Empty space between boxes in a stack is not deducted.
- Measurement is by external dimensions, including the pallet, crating and any protrusions. A pallet adds 12–15 cm of height, which is charged for too.
- Rounding up to whole centimetres in measurement and to the next 0.5 or 1 kg in weight is standard carrier practice.
- Compacting has the biggest effect in air freight. Repack the goods out of factory boxes into shipping cartons, remove empty space, reduce the height of the package — and volumetric weight falls along with the invoice. This has to be done at the warehouse in China, before departure.
- For very light goods, compare the modes. For cargo with a density of 100 kg/m³ sea freight wins several times over — which is exactly why furniture and packaging are almost never flown. The difference remains in transit time: sea around 70 days, rail 35–45, air from 10.
Volumetric weight is one of the two main reasons a rate cannot be quoted without dimensions. The other is the product category and the documents that go with it, covered on the page "What your rate depends on". Send us the weights and dimensions of your packages — we will calculate the chargeable weight for sea and air and show you where the difference in money is genuinely worth it.
FAQ
Frequently asked questions
Quote · free of charge
Not sure whether you will pay by weight or by volume?
Send the weights and dimensions of your packages — we will calculate the chargeable weight for sea, rail and air.