Carriers bill the larger of your box's real weight and a size-based weight. Enter your box to see what you will actually be charged, and how much of it is air.
Free. Uses the July 2026 USPS rules (divisor 139, every inch rounded up) and current UPS, FedEx and DHL rules.
Your box Rounded up by USPS+220 cu in from rounding
Sample box shown. Type your own size and weight below; the result updates instantly.
USPS · divisor 139
Priority Mail, Priority Mail Express, Ground Advantage, Parcel Select
Billable weight
23lb
You pay for 15 lb of air on every box.
A box 1 inch smaller on every side bills 4 lb less.
| USPS | ÷139 | 23 lb |
| UPS | ÷139 | 23 lb |
| FedEx | ÷139 | 23 lb |
| UPS Retail | ÷166 | 20 lb |
| DHL Express | ÷5000 | 10 kg |
On 12 July 2026 USPS cut its dimensional weight divisor from 166 to 139 and started rounding every fractional inch up. The same 18 × 14 × 12 in box went from 19 lb to 22 lb billable.
What changed and how to adjust your boxesEvery size compared across carriers, with the weight below which you are paying for empty space.
Work out total CBM for mixed carton sizes and how many 20ft, 40ft or 40ft High Cube containers you need, by volume and by weight.
Open the CBM calculatorDimensional (DIM) weight is a billing weight based on a package's size instead of what it weighs. Carriers multiply length, width and height, divide by a divisor, and charge you for whichever is greater: the DIM weight or the actual weight.
Since 12 July 2026 USPS uses 139 for Priority Mail, Priority Mail Express, Ground Advantage and Parcel Select, down from 166. It only applies to packages larger than 1 cubic foot (1,728 cubic inches), and fractional inches now round up to the next whole inch.
Round each side up to the next whole inch, multiply length x width x height, divide by the carrier divisor (139 for USPS, UPS Daily Rates and FedEx), and round the result up to the next pound. Your billable weight is the greater of that figure and the actual weight, also rounded up.
It usually isn't the divisor working against you there: UPS Retail Rates at the counter use 166, which gives a lower DIM weight than the 139 used on Daily Rates. The retail price per pound is higher, though, which is why shipping software with discounted commercial rates usually costs less overall.
Use the smallest box that protects the item, since every inch counts after rounding. Ship soft goods in poly mailers, keep USPS boxes at or under 1 cubic foot where possible, and ask your account manager about a higher contract divisor if you ship a lot of light, bulky parcels.