Chargeable Weight and Volumetric Conversion: Why Light Cargo Costs More

A pallet of feathers and a pallet of steel can carry the same freight bill, and the reason confuses many first-time shippers. Carriers sell a finite resource — either weight capacity or cubic space — and they charge for whichever one your cargo exhausts first. That number is the chargeable weight, and knowing how it is calculated tells you exactly what you are paying for.

Why carriers charge the greater of two numbers

An aircraft or a container has both a weight limit and a volume limit. Dense cargo fills the weight limit while leaving space; light, bulky cargo fills the space while leaving weight unused. To be paid fairly for whichever capacity you consume, the carrier compares your actual (gross) weight with a volumetric weight derived from your dimensions, and bills the higher of the two.

Air freight: divide by 6,000

Air freight uses a standard volumetric formula: length × width × height in centimetres, divided by 6,000, gives the volumetric weight in kilograms. A carton of 60 × 40 × 30 cm is 72,000 ÷ 6,000 = 12 kg volumetric. If that carton actually weighs 8 kg, you are charged for 12 kg — the volume "won". If it weighs 20 kg, you are charged for 20 kg — the weight won.

You are not paying for what your cargo weighs. You are paying for whichever capacity — weight or space — it uses up first.

Sea LCL: weight or measure

Ocean LCL works on the same principle but with a different yardstick, called weight or measure (W/M). The carrier compares the cargo's weight in tonnes against its volume in cubic metres, using the rule that 1 CBM equals 1,000 kg. Whichever is greater — the revenue tonne — is the billable unit. Light cargo is charged per CBM; heavy cargo is charged per tonne.

FCL: the box, not the scale

Full-container freight mostly escapes this logic — you pay a flat rate for the container regardless of how full it is — but weight still bites at the edges. Exceed the container's payload or the road-legal gross weight for trucking and you face overweight surcharges or a forced re-pack. So even in FCL, weight planning matters.

Worked examples

• Air, 1 carton 100 × 80 × 60 cm, 25 kg actual: volumetric = 480,000 ÷ 6,000 = 80 kg. You pay for 80 kg.
• LCL, 3 CBM weighing 1,200 kg: volume says 3 revenue tonnes, weight says 1.2 — you pay for 3.
• LCL, 1 CBM weighing 1,800 kg: weight says 1.8 revenue tonnes, volume says 1 — you pay for 1.8.

The lesson is simple: measure and weigh before you book, work out which number governs, and you will never be ambushed by a chargeable weight again.