How to Calculate Volumetric Weight
Why carriers bill for space, how the divisor changes what you pay, and how to work out whether your parcel is billed on actual or dimensional weight.
· 3 min read
A van has a fixed amount of space and a fixed weight limit, and it usually runs out of space first. A carrier that charged only by mass would lose money on every box of pillows and make a fortune on every box of bolts. So carriers calculate a second figure — volumetric weight, called desi in Türkiye — and bill whichever of the two is higher.
The formula
volumetric weight = (width × length × height) ÷ divisor
All three dimensions in centimetres. A 40 × 30 × 20 cm parcel is 24,000 cm³, and with a divisor of 3000 that is 8.
The divisor is the whole game
The divisor is set by the carrier, and it is the single number that decides how much a bulky parcel costs you:
| Divisor | Typical use | 24,000 cm³ becomes | | --- | --- | --- | | 3000 | Turkish domestic parcel carriers | 8.00 | | 4000 | Some domestic express services | 6.00 | | 5000 | International courier, air freight | 4.80 | | 6000 | IATA air cargo standard | 4.00 |
Same box, same contents, and the billed figure doubles between the top and bottom of that table. When you compare quotes, compare each carrier using its own divisor — a headline price per unit means nothing without it.
Chargeable weight
The carrier bills the higher of the two:
- Parcel is 40 × 30 × 20 cm and weighs 10 kg → volumetric 8, actual 10 → billed on 10.
- Same box weighing 3 kg → volumetric 8, actual 3 → billed on 8.
The second case is the one worth noticing. You are paying for five kilograms of air.
The volumetric weight calculator shows both numbers side by side and tells you which one will be used.
Measure the box, not the product
Carriers measure the outer packaging at its widest point, including tape, bulges and any protective wrap, and they round each dimension up to the next whole centimetre. A 29.2 cm side is measured as 30.
That rounding is why "just use a slightly smaller box" is such reliable advice. Dropping one dimension from 21 cm to 19 cm on a 40 × 30 parcel takes 2,400 cm³ off the calculation — most of a whole desi unit at divisor 3000.
Three ways to pay less
- Right-size the box. The most common waste is a product sitting inside a carton two sizes too big, padded out with filler.
- Ship flat where you can. Volume is a product of three numbers; halving the smallest one halves the result.
- Check the rounding boundary. If your parcel lands at 8.1 desi, finding two centimetres somewhere may drop it to a lower band.
Where this fits in your pricing
Shipping is one of the costs that decides whether a listing makes money. Once you know the chargeable weight and the tariff for that band, put it into the marketplace profit calculator with your commission rate and VAT to see what is actually left after a sale.