Dimensional weight (also called volumetric weight) is the weight a courier charges for based on the size of your box. In centimetres and kilograms the usual formula is length × width × height ÷ 5,000. The courier compares this with the actual weight and bills whichever is higher, called the chargeable weight.
Why couriers charge by size
A van or aircraft hold fills up by space long before it reaches its weight limit when parcels are light and bulky. A box of pillows takes the same room as a box of books but weighs far less. Dimensional weight makes sure large, light parcels pay for the space they use.
The formula and divisors
Measure the outside of the box, including any bulges, in centimetres. Multiply the three sides and divide by the courier’s divisor:
- ÷ 5,000 is the most common for international express shipping.
- ÷ 6,000 is used by some carriers and many domestic and economy services, which favours you.
- ÷ 4,000 is used by a few, which makes boxes count heavier.
- In inches and pounds: ÷ 139 for UPS and FedEx daily rates in the US, or ÷ 166 for some other services.
The same 50 × 40 × 30 cm box under different divisors:
| Divisor | Volumetric weight (kg) |
|---|---|
| 4,000 | 15 |
| 5,000 | 12 |
| 6,000 | 10 |
Always check your courier’s own rate card; the divisor is usually printed in the terms.
Measuring a box correctly
Measure the longest side as length, then width and height, all on the outside of the sealed box. Round each side up to the next whole centimetre, as couriers do. Include handles, label pockets and any bulge from overfilling. For odd shapes such as tubes or bags, measure the smallest rectangular box the item would fit in, because that is how it will be billed.
Worked examples (÷ 5,000)
Many couriers then round up to the next 0.5 kg. The chargeable weight below is the higher of actual and volumetric, rounded up that way:
| Box (cm) | Actual kg | Volumetric kg | Chargeable kg |
|---|---|---|---|
| 50 × 40 × 30 | 7 | 12 | 12 |
| 60 × 40 × 40 | 9 | 19.2 | 19.5 |
| 30 × 20 × 15 | 3 | 1.8 | 3 |
| 40 × 30 × 20 | 6.5 | 4.8 | 6.5 |
| 80 × 60 × 50 | 30 | 48 | 48 |
Take the first row. 50 × 40 × 30 = 60,000 cubic centimetres, ÷ 5,000 = 12 kg. The contents weigh only 7 kg, but you pay for 12. In the last row, the 80 × 60 × 50 box is 48 kg volumetric, so 30 kg of goods is still charged as 48 kg.
In inches, a 20 × 16 × 12 in box is 3,840 cubic inches, ÷ 139 = 27.6 lb, rounded up to 28 lb.
How to cut your shipping cost
- Right-size the box. Shrinking the 50 × 40 × 30 box to 45 × 35 × 25 drops the volumetric weight from 12 kg to 7.88 kg, which matters at every shipment. The box size calculator finds the smallest box for your product.
- Use less empty space. Less void fill means a smaller box. Choose padding that wraps the product rather than filling a big carton.
- Consider soft packaging. Clothes and textiles often ship well in poly mailers, which have little volume.
- Combine or split wisely. Two small dense boxes can cost less than one large light one, or the reverse. Run both options.
- Measure honestly. Couriers re-measure at the hub. A bulging box gets billed at its real size, sometimes with a correction fee.
- Compare divisors. A service using ÷ 6,000 charges about 17% less volumetric weight than one using ÷ 5,000.
Shipping by sea or in bulk
For air cargo the same idea applies, while sea freight is charged by cubic metres (CBM) or weight, whichever is greater. See our guide on how many cartons fit in a container for bulk shipments.
Work out any box quickly with the dimensional weight calculator or the volumetric weight calculator, then estimate the bill with the shipping cost calculator.
Frequently asked questions
How do I calculate dimensional weight?
Multiply length × width × height in centimetres and divide by 5,000 (or your courier’s divisor). In inches and pounds, divide by 139 or 166.
What is chargeable weight?
It is the higher of the actual weight and the dimensional weight. Couriers bill on this figure, often rounded up to the next 0.5 kg.
Why is my courier charging more than my parcel weighs?
Because the box is large for its weight, so its dimensional weight is higher than its actual weight. A smaller box usually fixes this.
Is the divisor 5000 or 6000?
Both are used. 5,000 is most common for international express; 6,000 is common for some domestic and economy services. Check your courier’s terms.