What volumetric weight is, and why carriers charge for it
A pillow and a paving slab can weigh the same on a scale, but the pillow fills far more of a truck or aircraft. If carriers priced on weight alone, light bulky shipments would be unprofitable — they fill the vehicle long before they fill its weight limit. So carriers convert a package's size into an equivalent weight, called the volumetric weight (also "dimensional weight", "DIM weight", or "cubic weight"), and bill on whichever is larger.
The formula
Volumetric weight = (Length × Width × Height) ÷ divisor
The divisor is the only moving part. It encodes how much space the carrier is willing to give you per unit of billed weight. A smaller divisor means a higher volumetric weight for the same box.
Chargeable weight is the one that costs you money
Chargeable weight = the greater of (actual weight, volumetric weight)
Weigh the shipment, calculate its volumetric weight, and compare. The bigger number is your chargeable weight. Dense cargo (machine parts, liquids, books) is usually billed on its actual weight; light cargo (apparel, foam, plastic goods, void-filled e-commerce boxes) is billed on its volumetric weight.
Which divisor should you use?
The divisor depends on the mode of transport and, sometimes, the specific carrier. These are the standard published values this calculator uses:
| Mode / carrier | Metric (cm, kg) | Imperial (in, lb) |
|---|---|---|
| Express courier (DHL, FedEx, UPS international) | ÷ 5000 | ÷ 139 |
| Air freight (IATA standard) | ÷ 6000 | ÷ 166 |
| Road freight (standard) | ÷ 4000 | ÷ 111 |
| Road freight (economy) | ÷ 3000 | ÷ 83 |
| Sea / ocean LCL | 1 m³ = 1000 kg | — |
The metric and imperial columns describe the same rule in different units: ÷5000 in cm/kg is identical to ÷139 in in/lb, and ÷6000 matches ÷166. When you switch units at the top of the calculator, it automatically applies the matching divisor so your chargeable weight stays the same. (Carriers publish the round numbers 139 and 166 rather than the exact unit conversion, and so does this tool.)
Air freight: the 6000 divisor and 1 CBM = 167 kg
Air cargo runs on the IATA standard divisor of 6000. Because one cubic metre is 1,000,000 cm³, dividing by 6000 means 1 CBM is treated as about 167 kg. That is the quick conversion freight forwarders use: multiply your cubic metres by 167 to get the volumetric weight, then compare to the gross weight. Some express integrators apply 5000 instead of 6000 for air parcels, which makes the same box "heavier" — worth checking when you compare two quotes.
Sea LCL is different
Ocean less-than-container-load (LCL) isn't billed in volumetric kilograms at all. It uses the revenue tonne: the greater of the weight in metric tonnes or the volume in cubic metres, charged at the per-CBM or per-tonne rate, whichever is higher (the 1 m³ = 1000 kg break-even). This calculator shows the equivalent figure so you can compare, but for detailed multi-leg freight quoting use a dedicated chargeable-weight tool.
A worked example
You're air-freighting two cartons of clothing, each 80 × 60 × 50 cm, with a combined scale weight of 45 kg.
- Volume per carton: 80 × 60 × 50 = 240,000 cm³
- Two cartons: 480,000 cm³ = 0.48 CBM
- Volumetric weight (air, ÷6000): 480,000 ÷ 6000 = 80 kg
- Actual weight: 45 kg
- Chargeable weight: the greater of the two = 80 kg
You pay for 80 kg even though the scale reads 45 kg, because the cartons are light for their size. Switch the same shipment to the ÷5000 express rule and the volumetric weight rises to 96 kg — the difference a divisor makes.
How to bring the number down
- Use the smallest box that genuinely fits — empty headroom is billed space.
- Remove bulky void fill; switch to thinner protective materials where safe.
- Consolidate several small parcels into one tighter carton.
- Watch the largest dimension: carriers round each side up, so trimming a stray centimetre can drop the whole shipment under a threshold.