Dimensional Weight Calculator
A light box in a big carton can bill like a heavy one. Enter the box and see the weight FedEx, UPS and USPS may charge for on a shipment within the U.S.
Enter all three sides to see the results.
Over the limit
Too big or too heavy for USPS parcels.
Past the ground parcel limits of 150 lb, 108 inches long or 165 inches in length plus girth. FedEx's guide says packages past its limits may be refused, returned to the shipper or disposed of. See freight.
Enter the weight
At or under 1 cubic foot, USPS goes by actual weight.
lb
estimated billable weight
No weight entered yet, so this is the dimensional weight alone.
At or under 1 cubic foot, USPS goes by actual weight.
This size or weight may add a handling charge, with at least 40 lb billed.
This size or weight may add an oversize charge, with at least 90 lb billed.
Over 108 inches in length plus girth, USPS may charge an oversized price.
Over 22 inches long or 2 cubic feet, USPS may add a nonstandard fee.
USPS charges its 70-pound price when dimensional weight runs higher.
This is an estimate of billable weight, not a price. The carrier's own measurement decides what goes on the bill.
How billable weight works
Multiply length, width and height in inches, then divide by the carrier's number. That is the dimensional weight. The carrier bills the bigger of that or what the scale says.
An 18 × 14 × 10 box comes to 2,520 cubic inches. Divide by 139 and round up, and you get 19 lb. If the pillow inside weighs 8 lb, the box bills at 19. A 6 × 6 × 6 box of books weighing 4 lb goes the other way: its dimensional weight is 2 lb, so it bills at the 4 lb on the scale.
Where the numbers come from
- FedEx's 2026 Service Guide, updated September 11, 2026, divides by 139 and rounds any fraction of an inch up.
- UPS lists 139 for daily rates and 166 for retail rates. The calculator shows 139, the heavier reading, and rounds fractions up.
- The USPS Domestic Mail Manual divides by 139 only when a rectangular parcel is over 1 cubic foot (1,728 cubic inches). That rule took effect July 12, 2026. It also sets the 70-pound price, the nonstandard fees and, for Ground Advantage, the oversized price over 108 inches.
- Handling and oversize triggers and the 40 and 90 lb minimums come from FedEx's guide. The calculator applies the same triggers to UPS as a cautious estimate, so check UPS's current guide for its exact figures.
Checked November 5, 2026. Carriers change these rules, and each carrier sets its own charges.
Things to check before you ship
- Measure the box after it is taped, at its widest point. A bulge counts.
- Any part of an inch rounds up, so 12.1 inches is billed as 13.
- Round tubes and soft packs can follow different rules. This calculator is for rectangular boxes.
- A carrier can re-measure a box in transit, and its measurement is the one on the bill.
Want it measured?
Bring the box to 9311 FM 1488 RD, Suite 30 in Magnolia, and we'll measure it and show you the options across carriers.