Guide
Dimensional weight: why a big light parcel is billed as a heavy one
Couriers and airlines sell space as well as weight. A parcel full of cushions fills as much of a van or aircraft hold as one full of books, but weighs a fraction as much, so charging by actual weight alone would lose money. The solution is to charge for the larger of two weights: the real one and a volumetric one worked out from the size. This page calculates both and tells you which one you will be billed for.
The formula
Volumetric weight is length × width × height divided by a number the carrier calls the divisor or dimensional factor. With centimetres the result is in kilograms, with inches it is in pounds. The larger the divisor, the lower the volumetric weight. The page offers four common presets: 5000 and 6000 for centimetres and kilograms, 139 and 166 for inches and pounds, and a box to type your carrier’s own figure.
Chargeable weight
Compare the volumetric weight with the actual weight of the packed parcel. Whichever is larger is the chargeable weight. Many carriers then round it up, to the next half kilogram or whole pound, which the page can do for you. The page tells you which weight sets the price, and if it is the volumetric one, how much weight you could take off the bill by making the box smaller.
A worked example
The default is a box of 40 × 30 × 20 cm that weighs 3.5 kg, with a divisor of 5000. Its volume is 24,000 cm³, so the volumetric weight is 4.80 kg. That is more than the actual weight, so the parcel is billed as 4.80 kg, 1.30 kg more than it weighs. Rounded up to the next half kilogram it would be 5.00 kg. A dense parcel of 25 × 20 × 15 cm that weighs 9 kg has a volume of 7,500 cm³ and a volumetric weight of 1.50 kg, so the actual 9.00 kg is charged and the box size does not matter. The US sample is a box of 18 × 14 × 12 inches weighing 12 lb with a divisor of 139. The volume is 3,024 in³, the volumetric weight 21.76 lb, and the chargeable weight, rounded up to a whole pound, is 22.00 lb, which is 9.76 lb above the real weight.
Saving money
If the volumetric weight is the one that counts, a smaller box is the only cure. Trimming 5 cm from two sides of the default box, to 35 × 25 × 20 cm, brings the volumetric weight down to 3.50 kg, level with the actual weight. Use the calculator to try a few box sizes, and consider whether padding or an oversized box is worth what it costs. For a batch of identical parcels, enter the number of packages and the page multiplies the chargeable weight.
Edge cases
Dimensions must be above zero. If you pick a metric divisor, enter centimetres and kilograms; for an imperial one, inches and pounds. Mixing them gives a meaningless result, so the field labels name both units and the results show the units of the rule you chose. A weight of zero is allowed, and then the volume always sets the price. Equal weights are reported as either.
Limits
Carriers publish their own divisors, which differ by service, country and sometimes by the size of the parcel. They also have minimum charges, size limits and rules for measuring that this page does not know. The result is an estimate of the weight that will be charged, not a quote, so confirm with the carrier’s rate card or an online quote before you promise a price to a customer.
Related tools
- CBM and Container Load Calculator does the same sums for pallets and cartons by the cubic metre.
- Shipping Label and Address Slip PDF Maker prints the label once you know the parcel.
- E-Commerce Profit Calculator adds shipping to the other costs of an order.
- Packing Slip and Delivery Note PDF Generator lists what is in the parcel you have just measured.
Checked against the current version of the Volumetric / Dimensional Weight Calculator on .