Dimensional weight calculator
Box size in inches (rounded up, as carriers do) and actual weight in pounds.
Box volume: 960 cubic inches
| Carrier | Divisor | Dimensional weight | You're billed for |
|---|---|---|---|
| USPS | 139 | not used under 1,728 in³ | 3 lb |
| UPS | 139 | 7 lb | 7 lb(size, not weight) |
| FedEx | 139 | 7 lb | 7 lb(size, not weight) |
Each carrier's rule for when dimensional weight applies is on its row in the table below the calculator. Divisors come from each carrier's own published rules.
How dimensional weight works
Carriers charge for the space a package takes up, not just its weight. They work out a “dimensional weight” from the box size and bill you for whichever is higher, the actual weight or the dimensional weight:
- Measure length, width and height in inches, rounding each up.
- Multiply them to get cubic inches.
- Divide by the carrier’s divisor (139 at USPS, UPS and FedEx) and round up to the next pound.
Example: a 12 × 10 × 8 inch box is 960 cubic inches. Divided by 139, that’s 6.9, rounded up to 7 lb. If the item inside weighs 3 lb, UPS and FedEx bill it as 7 lb. USPS bills the actual 3 lb, because the box is under one cubic foot.
Each carrier’s rule
| Carrier | Divisor | When it applies |
|---|---|---|
| USPS | 139 | Parcels over one cubic foot (1,728 cubic inches). Changed from 166 on July 12, 2026. USPS rules |
| UPS | 139 | May apply to all UPS package services. UPS 2026 daily rates |
| FedEx | 139 | Charged when dimensional weight exceeds actual weight. FedEx 2026 Service Guide |
Other surcharges to check
- Residential delivery: $6.50 per package at UPS and $6.45 at FedEx at list prices. USPS doesn’t publish one.
- Fuel: a weekly percentage at UPS (29.25%) and FedEx (28.75%) the week we checked.
- Address correction: $25.25 at UPS and $25.50 at FedEx if the address needs fixing.
- Long or large parcels at USPS Ground Advantage: $4.50 over 22 inches, $10 over 30 inches and $21 over two cubic feet.
See what these do to the total in the cheapest way to ship.
Get told when these prices change
Providers change fees with little notice. Alerts start soon, and we'll send nothing else.
Common questions
How do you calculate dimensional weight?
Multiply length by width by height in inches (each rounded up), divide by the carrier's divisor and round up to the next pound. USPS, UPS and FedEx all use 139 in 2026. You're billed for whichever is higher: the actual weight or the dimensional weight.
When does USPS charge dimensional weight?
Only for parcels bigger than one cubic foot (1,728 cubic inches), according to USPS's own rules. USPS changed its divisor from 166 to 139 on July 12, 2026. UPS and FedEx can apply dimensional weight to any package size.
How do I avoid dimensional weight charges?
Use the smallest box that fits the item safely. Cutting a box down by an inch on each side can drop the billed weight by a pound or more. Poly mailers work well for soft goods because they add almost no volume.