Free tool
Dimensional weight calculator
Enter the packed box and pick the carrier. The calculator uses each carrier's divisor, rounding rule and size floor as published on September 23, 2026, and flags the size lines that add fees.
Enter your box above.
What is billable weight?
Billable weight is the weight a carrier charges for: the higher of the package's scale weight and its dimensional weight, both rounded up to the next pound. Dimensional weight is length × width × height divided by the carrier's divisor, which is 139 at USPS, at UPS on Daily Rates and at FedEx as of September 2026.
Which divisor does each carrier use?
As of September 2026 the calculator uses 139 for USPS, UPS Daily Rates and FedEx, and 166 for UPS Retail Rates and for UPS and FedEx labels bought on eBay. USPS divides by 139 only above 1 cubic foot, and the eBay label divisors are per eBay's guide. Each carrier's dimensional weight divisor is built in.
| Carrier and rate | Divisor | Applies to |
|---|---|---|
| USPS Ground Advantage, Priority Mail, Priority Mail Express | 139 | Boxes over 1 cubic foot only |
| UPS Daily Rates | 139 | Any size |
| UPS Retail Rates | 166 | Any size |
| FedEx | 139 | Any size |
| UPS label bought on eBay | 166 | Over 1 cubic foot, per eBay's guide |
| FedEx label bought on eBay | 166 | Any size |
Sources: USPS DMM 283 and DMM 133 (July 12, 2026), the UPS Daily Rates guide (September 7, 2026) and Retail Rates guide, FedEx Service Guide 2026, and eBay's dimensional weight guide, checked September 23, 2026. The full carrier rules are on the 2026 divisors page.
How do you measure a box for shipping?
Measure the packed, taped box, not the item. Take each side at its widest point, bulges included, and call the longest side the length. USPS, UPS and FedEx all round any fraction of an inch up for dimensional weight, so 12.2 inches counts as 13. The calculator rounds up the same way.
Two USPS exceptions: for Ground Advantage Cubic tiers, USPS rounds each side down to the nearest quarter inch, and for its fee on boxes over 2 cubic feet it rounds to the nearest inch. The calculator applies both where they matter.
How do you read the result?
The calculator's result shows the billable weight first, then what set it: the scale weight, the dimensional weight or a surcharge minimum. Below that it lists any size lines the box crosses, and whether the box qualifies for Ground Advantage Cubic.
| Output | Use |
|---|---|
| Billable weight | The weight the carrier prices from. Use it when you set the listing's shipping |
| Set by | Dimensional weight means the box, not the item, sets the price. A smaller box that still fits would lower it |
| Box volume | Cut this and dimensional weight falls with it. One inch off each side of a 16 × 12 × 10 box takes it from 1,920 to 1,485 cubic inches |
| Length plus girth | Carriers set size limits and surcharges on this number |
| Flags | Size lines that add a fee, and whether the box qualifies for Ground Advantage Cubic |
| Over a limit | Over a carrier's weight or size limit, or in the USPS Oversized band (108 to 130 inches of length plus girth), the result says so in place of a billable weight |
What doesn't the calculator do?
The dimensional weight calculator doesn't quote prices. Those depend on the zone, the service and the rate you have, so check the label price in eBay's shipping calculator. It assumes a rectangular box. USPS multiplies the volume of a non-rectangular package by 0.785 first. It doesn't check the UPS and FedEx soft pack lines, 18 × 14 × 6 inches at UPS and 18 × 13 × 5 inches at FedEx.
How is billable weight calculated?
Why does USPS show no dimensional weight for my box?
Does this calculator work in centimeters?
Is the divisor the same for labels bought on eBay?
Disclosure Shipping for Sellers is published by the team behind FlowLister, AI eBay listing software that turns item photos into complete eBay listings, shipping included. It's AI, so it misses things: weigh and measure the packed box before you trust any shipping number, ours included. We make FlowLister, so read this as a disclosure, not a recommendation.