Every vehicle, aircraft and container has two limits: weight and space. Volumetric weight — also called dimensional or “dim” weight — converts the space a shipment uses into an equivalent weight, so light, bulky goods pay their fair share. The chargeable weight is the greater of the actual weight and the volumetric weight.
We introduced chargeable weight in an earlier article. This guide goes deeper for freight operators: the factors used in each mode, how to measure properly and worked examples you can use to train your team.
The formula
The divisor (or its inverse, the density factor in kg per cubic metre) depends on the mode of transport and on your contract with the carrier.
| Mode | Common divisor (cm³ per kg) | Same as (kg per m³) | Notes |
|---|---|---|---|
| Express / courier | 5,000 | 200 | Some networks use 4,000 for certain services |
| Air cargo (IATA standard) | 6,000 | ≈ 167 | Per shipment, on total volume |
| Road freight / pallet networks | 3,000–4,000 | 250–333 | Varies widely by carrier and country — check your terms |
| Road freight (Europe, full width) | By loading metre | ≈ 1,750 kg per LDM | Used for non-stackable or floor-loaded freight |
| Sea freight LCL | W/M: 1 m³ = 1,000 kg | 1,000 | Charged per revenue ton: the greater of tonnes and cubic metres |
| Imperial (lb, inches) | 139 or 166 in³ per lb | — | 139 is common for express/domestic, 166 for international and air |
How to measure properly
- Measure at the widest points, including bulges, handles, labels sticking out and pallet overhang.
- Include the pallet in the height and footprint of palletised freight.
- Round up each dimension to the next whole centimetre (or inch), as most carriers do.
- Irregular shapes — tyres, rolls, machinery — are measured as the smallest rectangular box they fit in.
- Non-stackable freight is often charged to the full height of the vehicle or container space it blocks.
- Round the result as the carrier does: often up to the next 0.5 kg for parcels and the next whole kg for freight.
Worked example 1: an express carton
Worked example 2: a multi-piece air cargo shipment
For air cargo, volumetric weight is normally calculated on the total volume of the shipment, then compared with the total actual weight.
Worked example 3: a pallet by road
Worked example 4: sea freight LCL
Worked example 5: imperial units
Weight breaks: when charging more weight costs less
Air cargo rates usually fall as weight increases, in bands called weight breaks (for example under 45 kg, 45 kg, 100 kg, 300 kg, 500 kg, 1,000 kg). Sometimes it’s cheaper to charge a shipment at the next break’s minimum weight than at its own weight.
Using density to plan loads
Volumetric weight is also a planning tool. Shipments heavier than the density factor “weigh out” a vehicle or container before it’s full; lighter ones “cube out” before the weight limit is reached. Mixing the two fills both limits.
This is the logic behind consolidation: combining shipments of different densities so you sell both the weight and the space you’ve paid for.
Common mistakes
- Using the customer’s declared dimensions without checking at receiving.
- Mixing divisors between staff, branches or services.
- Calculating air cargo volume per piece and rounding each piece up, instead of on the total.
- Forgetting the pallet base, or measuring a bulging carton at its flat sides.
- Not passing carrier re-weigh and re-measure adjustments on to the customer.
- Pricing sea LCL on weight alone.
Make it consistent
Publish your divisors and measuring rules in your terms, train every receiving team the same way, and let your system do the arithmetic: dimensions in, chargeable weight and price out. Most disputes disappear when the same rule is applied every time. Operators quoting multi-piece air shipments rely on air cargo software that applies the divisor and weight breaks automatically, and pallet carriers on LTL freight software that charges by weight, volume or pallet — whichever the rate card says.