Pricing reference
Volumetric weight, and why a light parcel can cost more
Volumetric weight is length × width × height divided by a carrier-specific divisor: commonly 139 for inches and pounds, or 5,000 for centimetres and kilograms. You are charged on the greater of volumetric weight and actual weight. That figure is the chargeable weight.
The formula
Carriers sell space as much as they sell mass. A pallet of feathers and a pallet of bricks occupy the same slot on an aircraft, so pricing on mass alone would let bulky freight travel almost free. Volumetric weight converts the space a parcel takes up into a comparable weight figure.
Imperial (inches, pounds)
(length × width × height) ÷ 139 = volumetric weight in lb
Metric (centimetres, kilograms)
(length × width × height) ÷ 5,000 = volumetric weight in kg
The divisor is the variable that matters. It is set per carrier and often per service, and a lower divisor means a higher volumetric weight for the same box. Every quote we return states the divisor it used, so a comparison is genuinely like-for-like.
Worked examples
| Shipment | Dimensions | Actual | Divisor | Volumetric | Charged on |
|---|---|---|---|---|---|
| Cushions in a large box | 24 × 18 × 18 in | 3 lb | 139 | 56 lb | 56 lb |
| Books, tightly packed | 12 × 10 × 8 in | 22 lb | 139 | 7 lb | 22 lb |
| Laptop, retail box | 18 × 14 × 4 in | 6 lb | 139 | 8 lb | 8 lb |
| Trainers, metric | 40 × 30 × 15 cm | 1.8 kg | 5,000 | 3.6 kg | 3.6 kg |
The pattern is consistent: dense parcels are charged on actual weight, and anything light in a large box is charged on volume. The cushions in row one weigh 3 lb and are billed at 56 lb. An eighteen-fold difference caused entirely by the box.
How to calculate it, step by step
Measure the parcel at its widest points
Measure length, width and height including any bulge, tape or handle. Carriers measure the box as it arrives, not as it was designed, and round each dimension up to the next whole unit.
Multiply the three dimensions
Length × width × height gives the cubic volume of the parcel.
Divide by the carrier's divisor
Divide the volume by the divisor the carrier applies to that service. Commonly 139 for inches and pounds, or 5,000 for centimetres and kilograms.
Compare against actual weight
You are billed on the greater of the two, which is the chargeable weight. If volumetric exceeds actual, the parcel is 'light and bulky' and repacking smaller is usually cheaper than negotiating a rate.
FAQ
Volumetric weight questions
What is volumetric weight?
Volumetric weight: also called dimensional or DIM weight, is a parcel's volume converted into a weight figure, so that a large, light parcel pays for the space it occupies on a vehicle or aircraft. It is calculated as length × width × height ÷ a carrier-specific divisor.
Which divisor applies to my shipment?
The divisor is set by the carrier and varies by service and region. 139 is common for imperial measurements in inches and pounds, and 5,000 for metric measurements in centimetres and kilograms; some air services use 6,000 and some domestic ground services use 166. The quote screen shows the divisor used for each carrier's price rather than assuming one.
Am I charged on actual weight or volumetric weight?
Whichever is greater. That figure is the chargeable weight. A 20 kg dense parcel is charged at 20 kg; a 3 kg parcel of cushions in a large box may be charged at 12 kg.
Does rounding matter?
Yes, and it is the most common source of an unexpected surcharge. Most carriers round each dimension up to the next whole centimetre or inch before multiplying, then round the resulting weight up to the next increment. A box measured at 30.2 cm is treated as 31 cm.
How do I reduce volumetric weight?
Use the smallest box the contents safely allow, remove void fill you don't need, and avoid oversized outer cartons for small items. Cutting each dimension by 10% cuts the volume by roughly 27%, which is usually a bigger saving than any rate negotiation.