What is dimensional weight?

Dimensional weight, also called volumetric weight, prices a package by the space it occupies rather than its scale weight. Carriers bill the greater of actual weight and dimensional weight so that large but light parcels pay their fair share of trailer space.

What divisor should I use?

FedEx and UPS use 139 for US domestic shipments (cubic inches divided by 139 equals pounds). DHL and most international air freight use a metric divisor of 5000 or 6000 (cubic centimetres per kilogram). USPS uses 166 for larger zones. Always confirm your current contract rate.

How do carriers round DIM weight?

Carriers round the calculated dimensional weight up to the next whole pound or kilogram, and they round each measured dimension up to the next whole unit before multiplying. This tool rounds the final DIM weight up to match.

Which weight am I actually billed on?

You are billed on the billable weight, which is the greater of the actual weight and the dimensional weight. If your box is oversized for its contents, the DIM weight wins and you pay more than the scale suggests.

How do I lower my dimensional weight?

Use a smaller box. Shrinking each dimension cuts volume fast because volume is the product of all three. Eliminating void fill and right-sizing cartons is the single biggest lever for reducing DIM-based charges.

Dimensional Weight Calculator

If your parcel is large but light, carriers do not bill you on the scale weight — they bill on dimensional weight, the space the box takes up in the trailer. This calculator applies each carrier’s divisor, rounds the result the way they do, and tells you which weight you actually pay on.

How it works

Dimensional weight converts volume into a weight using a divisor:

imperial: DIM weight (lb) = (L × W × H in inches) / divisor
metric:   DIM weight (kg) = (L × W × H in cm)     / divisor
billable weight = max(actual weight, DIM weight)

Common divisors are 139 for FedEx and UPS US domestic, 166 for USPS in higher zones, and 5000 or 6000 for DHL and IATA air freight in metric. The carrier rounds the dimensional weight up to the next whole unit, which this tool does too, and then charges on whichever is larger — actual or dimensional.

Example and tips

An 18 by 14 by 12 inch box has a volume of 3024 cubic inches. Divided by 139 that is 21.8, rounded up to a 22 lb dimensional weight. If the parcel actually weighs 5 lb, you are still billed on 22 lb. Drop the box to 14 by 12 by 10 inches and the DIM weight falls to 13 lb — a sizeable saving for the same contents. Right-sizing cartons and cutting void fill is the most effective way to keep dimensional charges down.