Carriers charge for whichever is greater: a parcel's actual weight or its volumetric weight. This figure is the billable weight (also called chargeable weight).
- Actual weight — the parcel's weight on a scale.
- Volumetric weight — a weight calculated from the parcel's dimensions, reflecting how much space it takes up in transit.
A parcel that is large but light still occupies as much space on a vehicle or aircraft as a smaller, heavier one, so carriers bill on size as well as weight.
Billable weight = greater of (actual weight, volumetric weight)
This article covers international shipping services only.
How volumetric weight is calculated
Volumetric weight = (Length × Width × Height) ÷ DivisorThe divisor (also called the DIM factor) is set by the carrier. A lower divisor produces a higher volumetric weight, so it has a direct effect on shipping cost.
International divisors by carrier
Carrier | Services | Inches → lbs | cm → kg |
FedEx | International Priority, International Economy, International Connect Plus | 139 | 5,000 |
UPS | Worldwide Express, Worldwide Expedited, Worldwide Saver | 139 | 5,000 |
DHL Express | All international services | 139 | 5,000 |
Two things to watch for
1. 139 and 5,000 are not interchangeable
139 in³/lb and 5,000 cm³/kg are often quoted as if they were the same standard in different units, but they aren't:
- 139 in³/lb ≈ 5,721 cm³/kg
- 5,000 cm³/kg is therefore the stricter figure
Billing a shipment in kg at a 5,000 divisor produces roughly 14% higher volumetric weight than billing the same parcel in lbs at a 139 divisor. Where a carrier offers a choice of billing unit on an international lane, this is worth checking.
2. Rounding rules differ between carriers
Carrier | How rounding works |
FedEx | Each dimension is rounded up to the next whole inch/cm before dividing |
UPS | Each dimension is rounded up to the next whole inch/cm before dividing |
DHL Express | Divides on the measured dimensions, then rounds the final chargeable weight up to the nearest 0.5 kg |
Worked example
A carton measuring 40 × 30 × 25 cm with an actual weight of 4 kg:
- Volume = 40 × 30 × 25 = 30,000 cm³
- Volumetric weight = 30,000 ÷ 5,000 = 6 kg
- Actual weight = 4 kg
- Billable weight = 6 kg
The shipment is billed at 6 kg, despite weighing 4 kg, because the parcel is light relative to its size.
Why this matters
- Shipping cost estimates based on actual weight alone understate cost for bulky or lightweight product categories, such as apparel, footwear, and homeware.
- Reducing packaging size — right-sizing cartons and cutting void fill — is often the fastest way to lower billable weight and shipping cost.
- Contracted divisors vary. High-volume shippers can negotiate more favourable divisors with their carrier (166, 194, 200+ on FedEx/UPS; DHL will move off 5,000 at volume). Check the divisor in your own carrier contract rather than assuming the standard rate applies.