If you have ever been quoted for 9 kg on a parcel that weighs 3 kg on your bathroom scales, you have met volumetric weight. It catches people out constantly, and it is worth understanding before you order rather than after.
The formula
Air carriers bill on chargeable weight, which is whichever is greater: the actual weight, or the volumetric weight.
Volumetric weight (kg) = length × width × height in centimetres, divided by 5000.
A box 40 × 30 × 25 cm is 30,000 cubic centimetres, which is 6 kg volumetric. If the contents weigh 3 kg, you are billed for 6.
Why it exists
An aircraft runs out of space long before it runs out of weight allowance. A pallet of pillows and a pallet of books occupy the same floor, so charging only by weight would mean the pillows travel almost free. Every carrier in the world prices this way.
What it means in practice
Some things are almost always billed on volume: cushions, soft toys, clothing in retail boxes, empty containers, anything padded. Some things are almost never billed on volume: books, ceramics, oils, tools, electronics.
How to bring it down
- Let us repack. Retail boxes are designed for shelves, not aircraft. Removing them routinely takes a third off the volume.
- Consolidate. Five small boxes have five sets of walls and five air gaps. One box has one.
- Say what can be compressed. Textiles can often be vacuum-packed. Tell us in the shipping instructions and we will do it.
- Measure before you order. The calculator takes box dimensions, so you can see the volumetric effect before you spend anything.
A worked example
Three parcels — a saree box 45 × 35 × 12 cm, a shoe box 33 × 22 × 12 cm, and a book parcel 25 × 20 × 10 cm — total about 5.2 kg actual and 5.6 kg volumetric shipped separately. Repacked into one 45 × 35 × 22 cm carton they come to 6.9 kg volumetric but pay one shipping charge instead of three, which is where the saving comes from.