Volumetric weight, and why your cheap parcel got expensive
Couriers bill the space a box occupies, not just what it weighs. Here is the formula, the rounding rule, and the packing change that usually pays for itself.
Every international courier bills on billed weight, which is the higher of two numbers: what the parcel actually weighs on a scale, and what it would weigh if it were as dense as the courier assumes. The second number is volumetric weight, and it is the one that surprises people.
The formula
Length x breadth x height in centimetres, divided by 5000, gives volumetric weight in kilograms. A 40 x 30 x 20 cm box is 24000 cubic centimetres, which is 4.8 kg volumetric — regardless of whether it holds scarves or ball bearings.
If your parcel weighs 2 kg but measures 4.8 kg volumetric, you are billed 4.8 kg. Air freight sells space before it sells mass.
Then it rounds up
Rate cards are slab-based. A billed weight of 4.8 kg does not cost 4.8 times the per-kilo rate; it lands in the 5 kg slab and is charged at that slab's price. Crossing a slab boundary by fifty grams costs the same as crossing it by half a kilo, which is why shaving packaging right at a boundary is the highest-leverage change available to most sellers.
What to do about it
- Measure the outer carton after sealing, not the product. Tape and void fill count.
- Cut the box down to the contents rather than filling a standard size with air.
- Check where your billed weight sits against the next slab before you pack a second unit in.
- Use poly mailers for soft goods — they take the shape of the contents instead of dictating it.
In the ShipGoPick portal the volumetric and billed weight are both computed server-side as you type the dimensions, and the quote you see is the slab you will actually be charged for. There is no second calculation at booking.
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