Volumetric weight: why a light box can cost more
A courier van fills up with space long before it fills up with weight. So couriers charge for whichever is greater: the real weight of your parcel or its volumetric weight, which is a weight worked out from its size.
The formula
Most couriers use the same calculation. Multiply length × width × height in centimetres and divide by 5,000. The result is the volumetric weight in kilograms.
length × width × height ÷ 5,000 = volumetric weight (kg)
Some services use a different divisor, such as 4,000 or 6,000, but 5,000 is the most common. Try it with our free volumetric weight calculator.
Worked examples
| Parcel | Size (cm) | Real weight | Volumetric | Charged as |
|---|---|---|---|---|
| Shoebox | 33 × 20 × 12 | 1.2 kg | 1.6 kg | 1.6 kg |
| Duvet in a box | 50 × 40 × 30 | 3 kg | 12 kg | 12 kg |
| Books | 30 × 20 × 15 | 6 kg | 1.8 kg | 6 kg |
The duvet shows the trap. It only weighs 3 kg, but the box is big enough to be charged as 12 kg.
How to keep big, light parcels cheap
- Use the smallest box that fits. Every centimetre counts, because the three sides multiply together.
- Soft items such as clothes and bedding can go in a strong mailing bag, which takes up far less space than a box.
- Vacuum bags work well for duvets and pillows.
- Compare couriers. They do not all treat size the same way, and Kargom prices your exact size and weight with each one.
Related guides
The cheapest way to send a parcel in the UKLive prices from Evri, InPost, Royal Mail, Yodel and DPD for parcels from 0.5 kg to 30 kg, plus five ways to pay less every time you send.How to package a parcel so it arrives in one pieceA practical checklist: choosing a box, padding, taping and labelling, plus what to do with fragile items and liquids.Drop-off or collection: which should you choose?The real difference in price, time and hassle between dropping a parcel at a shop or locker and booking a courier to collect it.