Volumetric weight, and why your small parcel cost so much

An aircraft runs out of room before it runs out of lift

A cargo hold has a fixed volume and a fixed weight limit, and on most passenger routes the volume is exhausted first. If carriers billed on mass alone, a pallet of pillows would occupy half a hold and earn almost nothing.

So the industry prices on whichever is greater: what the parcel actually weighs, or what that much space would weigh if it were filled with something of average density. The second figure is volumetric weight.

The formula

Multiply length by width by height in centimetres, then divide by the carrier’s divisor. Express and Priority use 5000. Economy Air uses 6000, which is why a bulky box is proportionally cheaper on the slower lane.

A 40 × 30 × 25 cm box is 30,000 cubic centimetres. Divided by 5000 that is 6 kg of volumetric weight. If the contents weigh 2 kg, you are billed for 6 kg. You are paying for air.

Chargeable weight = the greater of actual and volumetric, rounded up to the next half kilogram.

What actually reduces it

Retail packaging is designed for shelves, not aircraft. A pair of shoes arrives in a box sized for display, inside a courier bag sized for the box. Strip both and the same shoes take a third of the space.

Soft goods are the best void fill there is. Clothing packed around a hard item removes the empty corners that a rigid box would carry across an ocean.

This is why our repack is free rather than a paid extra. It reduces the number we bill you on, and a customer who feels overcharged does not come back.

When the maths flips

Dense items — books, tools, jewellery, spare parts — are billed on actual weight and benefit from nothing you do to the box. For those, consolidation is where the savings are, not repacking.

Light and bulky items — bedding, cushions, lampshades, empty containers — are billed on volume, and repacking is worth more than consolidation. Your locker flags which case each parcel falls into.