Free tool · UPS, FedEx, and USPS
Dimensional weight calculator
Enter your box size and weight to see what UPS, FedEx, and USPS will actually bill you for, including the July 2026 USPS change. Nothing you type is saved.
| Carrier | Dim weight | Billable | Billed on |
|---|
Shipping is part of your true cost per unit.
TrueLanded's Pricing tab includes fulfillment and shipping per unit, so your margin reflects what you really pay.
How it works
How dimensional weight is calculated
1. Round each side up
All three carriers round every measurement up to the next whole inch. A 12.1 inch side counts as 13, so a fraction of an inch can add pounds.
2. Divide by the divisor
Multiply the rounded sides to get cubic inches, then divide by the carrier's divisor (139 for UPS daily rates, FedEx, and USPS) and round up to the next pound.
3. Pay the higher weight
The carrier bills whichever is higher: the actual weight, rounded up to the next pound, or the dimensional weight. A light item in a big box pays for the space.
Published rules, October 2026
| Carrier | Divisor | When it applies | Rounding |
|---|---|---|---|
| USPS | 139 (166 before July 12, 2026) | Only packages over 1 cubic foot (1,728 cubic inches): Priority Mail, Priority Mail Express, Ground Advantage, and Parcel Select | Each side up to the next inch (since July 12, 2026) |
| UPS | 139 daily rates, 166 retail | Every package | Each side up to the next inch |
| FedEx | 139 | Every package | Each side up to the next inch (since August 2025) |
Negotiated rates often use a different divisor, so check your rate agreement and enter it above. Carriers update their rules, usually each January; confirm against the carrier's current service guide. Under 1 pound, USPS Ground Advantage prices by the ounce.
Ways to lower your billable weight
Shave the fractions
Because every side rounds up, a box that measures 12.1 inches bills like 13. Choosing a box a quarter inch smaller can drop a full pound or more.
Stay under 1 cubic foot for USPS
USPS ignores dimensional weight up to 1,728 cubic inches, about a 12 × 12 × 12 box. Small, heavy items often ship cheapest there.
Right-size your box range
Stock a few sizes that fit your best sellers closely, and use poly mailers for soft goods. Less empty space means less air on your invoice.
What is dimensional weight?
Dimensional (DIM) weight is a billing weight based on a package's size instead of its scale weight. Carriers use it so that large, light boxes pay for the space they take up on a truck or plane.
What changed at USPS in July 2026?
On July 12, 2026, USPS lowered its dimensional weight divisor from 166 to 139, matching UPS and FedEx daily rates, and began rounding each side up to the next whole inch. Packages over 1 cubic foot can now bill noticeably heavier than before.
Is my data saved?
No. The calculator runs entirely in your browser, and nothing you type is stored or sent anywhere.
Does this calculate shipping prices?
No. It shows the weight you'll be billed at. Your price then depends on that weight, the shipping zone, the service, your rates, and any surcharges.