SuanSupplyWhat is dimensional weight?
Dimensional weight (also called DIM weight or volumetric weight) is the weight a carrier assigns to a parcel based on its size. A big, light box takes up space in a truck or plane, so carriers price it as if it were heavier. They compare the dimensional weight with the actual weight and charge for whichever is higher: that number is the billable weight.
How do you calculate dimensional weight?
Measure the packed box, round each side up to a whole inch (or centimetre), multiply the three sides and divide by the carrier's divisor:
Example (the calculator's default numbers): an 18 × 14 × 10 inch box is 2,520 cubic inches. With the UPS daily-rate and FedEx divisor of 139, that is 2,520 ÷ 139 = 18.1, rounded up to 19 lb. The box only weighs 9 lb, so you pay for 19 lb. At UPS retail rates (divisor 166) the same box is 16 lb.
In metric: a 46 × 36 × 26 cm box is 43,056 cm³. Divided by 5,000 (UPS and FedEx), that is 8.6, rounded up to 9 kg, against 4 kg on the scale.
Which divisor does each carrier use?
A smaller divisor means a higher dimensional weight. These are the published divisors as of October 12, 2026:
| Carrier | Inches / pounds | Centimetres / kilograms | Applies to |
|---|---|---|---|
| UPS, daily rates | 139 | 5,000 | Most UPS account shipments |
| UPS, retail rates | 166 | - | Rates at the counter |
| UPS Canada, domestic air | 115 | 4,100 | Air shipments within Canada |
| FedEx | 139 | 5,000 | Billed on whichever is greater, actual or dimensional |
| USPS Priority Mail and Ground Advantage | 139 | - | Only parcels over 1 cubic foot (1,728 cubic inches); rule revised July 12, 2026 |
USPS changed its rule on July 12, 2026: parcels over 1 cubic foot are now divided by 139. Nonrectangular parcels (tubes, odd shapes) have a separate rule with an adjustment factor of 0.785. Canada Post, Royal Mail, Correos de México and other carriers set their own rules: check theirs and enter the divisor in the calculator.
Why is my shipping quote higher than the billable weight suggests?
Billable weight only picks the weight band. The final price also depends on the service (ground, express, international), the distance or zone, fuel surcharges, residential delivery and extra handling for large or heavy boxes. That is why exact rates need a live quote from the carrier or a shipping platform.
How can you lower your dimensional weight?
- Use the smallest box that protects the item. Every inch you cut on each side lowers the volume fast.
- Measure after packing, including bulges: carriers measure the box at its widest points.
- Try poly mailers for soft goods such as clothing, where the bag shrinks to the item.
- Check the 1 cubic foot line on USPS: a box at or under 1,728 cubic inches is charged on actual weight only.
- Compare carriers on the same box. The calculator's table shows how the rules differ.
Where can you get exact rates?
Once you know the billable weight, get live quotes for the actual route and service. Importing stock first? Work out the full cost per unit with our landed cost calculator, and read how freight from China works in our guide to shipping from China.
Our pick for live shipping rates: Easyship
Easyship compares rates from many couriers in one place, with discounted rates, and shows import duties and taxes before you book. It works for sellers in the US and Canada. See how it compares with Pirate Ship and ShipStation in our comparison guide.
Frequently asked questions
What is the dimensional weight divisor for UPS and FedEx?
139 cubic inches per pound for UPS daily rates and FedEx, and 166 for UPS retail rates. In metric, UPS and FedEx use 5,000 cubic centimetres per kilogram (as of October 12, 2026).
Does USPS charge dimensional weight?
Yes, for Priority Mail and USPS Ground Advantage parcels over 1 cubic foot (1,728 cubic inches). Since July 12, 2026 the divisor for those parcels is 139. Smaller parcels are charged on actual weight.
Is billable weight the higher or the lower weight?
The higher one. Carriers compare the dimensional weight with the actual weight and charge whichever is greater.
How do I calculate volumetric weight in kg?
Multiply length × width × height in centimetres and divide by the carrier's metric divisor, 5,000 for UPS and FedEx. A 46 × 36 × 26 cm box is 43,056 ÷ 5,000 = 8.6, rounded up to 9 kg.
Can this calculator give me a shipping price?
No. It gives the billable weight, which decides the price band. Prices depend on service, zone and surcharges, so get a live quote for the exact route.
This calculator gives billable weight for planning, not prices. Carriers change their rules; check the carrier's own page before relying on a number. We are not affiliated with UPS, FedEx or USPS.