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Dimensional weight calculator: what each carrier bills for your box
A box 14 x 10 x 6 inches, 4 lb on the scale
7 lb at FedEx The same box bills 4 lb at USPS, 6 lb at UPS Retail Rates and 7 lb at UPS Daily Rates. Each carrier bills the heavier of the scale weight and length x width x height divided by its own number, 139 or 166. USPS Ground Advantage only counts size above 1,728 cubic inches.
Rules read in the carriers' own documents on Nov 5, 2026: USPS Domestic Mail Manual, FedEx Service Guide (updated Sep 11, 2026), UPS 2026 Daily and Retail Rate & Service Guides (updated Sep 7, 2026). How we test ยท How we are paid: no carrier has paid for this page.
Your box
Weights only, no prices. Sides are rounded up to whole inches first, as each carrier's steps say; the odd-shape choice changes the USPS line only. Under 1 lb USPS prices in ounce steps, so the weight is shown as entered. Estimate from published rules: a carrier's scanner has the last word.
How each carrier counts it
| Carrier | Which boxes | Divides by | Rounding | Source |
|---|---|---|---|---|
| FedEx | Every package in your own box | 139 | Sides up to the next inch; any fraction of a pound up | Service Guide, p. 135, updated Sep 11, 2026 |
| UPS Daily Rates | Any package (UPS says it may apply). For shippers with a UPS account: the guide gives Daily Rates to accounts opened since July 11, 2016 | 139 | Sides up to a whole number, at least 1 inch; scale weight and any fraction up to the next pound | 2026 Rate & Service Guide, p. 19, updated Sep 7, 2026 |
| UPS Retail Rates | Any package (UPS says it may apply). For shippers who do not receive Daily Rates, such as shipping from a UPS location with no account | 166 | Same as Daily Rates | 2026 Rate & Service Guide, p. 19, updated Sep 7, 2026 |
| USPS Ground Advantage | Only boxes over 1,728 cubic inches | 139 | Sides up to a whole inch; dimensional weight up to the next pound; any fraction of a pound is a whole pound from 1 lb; billed at most the 70-pound price | Domestic Mail Manual 133 and 283, marked 7-12-26 |
Which UPS row is yours: UPS's guide gives Daily Rates to shippers who open a UPS account, and its rates page adds a scheduled pickup or a UPS contract; Retail Rates are for shippers who do not receive Daily Rates, such as shipping from a UPS location without an account or occasionally with a card. We have not found UPS saying which one a shipping platform's label follows, so we do not say. The nightly price check cannot read UPS or FedEx documents; a person re-reads them when a new guide appears.
The USPS line at 1 cubic foot
At or under 1,728 cubic inches USPS Ground Advantage bills the scale weight, with any fraction of a pound counted as a whole pound. Over it, size starts to count. A 12 x 12 x 12 inch box is exactly on the line and bills the 2 lb on the scale. Make it 12 x 12 x 13 and the same 2 lb box bills 14 lb. The smallest whole-inch box over the line, 7 x 13 x 19, bills at least 13 lb.
USPS Ground Advantage Commercial cubic prices work the other way. For commercial customers, they need a package of 1 cubic foot or less, 20 lb or less and 22 inches or less on the longest side, not a roll or tube, and they round each side down to the nearest quarter inch, where the dimensional weight steps round up to a whole inch.
Not a box? For a nonrectangular parcel USPS multiplies the volume by 0.785 first. A 24 x 12 x 10 inch, 5 lb parcel bills 17 lb instead of 21 lb. FedEx and UPS state no such factor; UPS says to treat an irregular package as if it were in a regular rectangular box. Tubes and other round items also pay an Additional Handling charge at both.
Long boxes pay a minimum
FedEx and UPS add an Additional Handling charge, and bill at least 40 lb, when the longest side is over 48 inches, the second-longest is over 30, length plus girth is over 105 (girth is two times the width plus two times the height) or the box is over 10,368 cubic inches. A 49 x 6 x 6 inch, 5 lb box has a dimensional weight of 13 lb but bills 40 lb. Over 10,368 cubic inches the size rule alone already gives 63 lb or more, so for a slim box the length is what triggers the minimum. We do not price the charge here.
Quick answers
What is dimensional weight?
Carriers bill for the space a box takes up as well as its weight. They multiply length x width x height in inches, divide by a number set by the carrier, and bill the heavier of that result and the scale weight. For the example box, 14 x 10 x 6 in and 4 lb, FedEx bills 7 lb.
Do UPS, FedEx and USPS use the same divisor?
FedEx divides by 139. UPS divides by 139 on Daily Rates and 166 on Retail Rates. For Ground Advantage, USPS divides by 139, and only for boxes over 1,728 cubic inches. We did not read other USPS services. Rules read Nov 5, 2026.
Does USPS charge dimensional weight on every box?
No. For USPS Ground Advantage the size rule starts above 1 cubic foot (1,728 cubic inches). At or under that line USPS bills the weight on the scale, rounded up to a whole pound from 1 lb. Over it, USPS bills whichever is larger, the scale weight or the dimensional weight, up to the 70-pound price.
Which UPS divisor applies to me?
UPS's guide gives Daily Rates to anyone who opens a UPS account, plus older Daily Rates holders, and says shippers who do not receive Daily Rates are charged Retail Rates. Its rates page adds that Retail Rates apply if you ship from a UPS location with no payment account or scheduled pickup, or ship infrequently with a payment card. Daily Rates use 139; Retail Rates use 166 for domestic packages.
Not for you if
- You ship from CanadaWe read the US rules only. UPS Canada and Canada Post publish their own, which we have not read.
- You ship pallets or freightFreight has its own weight rules. This page is for parcels.
- You need a price, not a weightThis page works out the billed weight. The price of a label depends on your zone, your account and your platform.
How we know
- We read USPS Domestic Mail Manual 133 and 283, the FedEx 2026 Service Guide and the UPS 2026 Daily and Retail guides, and checked each rule against the page.
- The USPS dimensional weight steps carry the manual's revision marker [7-12-26]. We have not read the version before it, so we do not say what changed.
- UPS's 2026 Daily and Retail guides carry this update date. UPS publishes new guides each year; we have not read any 2027 UPS information, so the UPS rows are for 2026 until we re-read them.
The example box and the USPS line figures on this page come from the same calculator code you can use above. It is tested against worked examples for each rule it applies, including the line at 1,728 cubic inches, the 70-pound price, the 0.785 factor and the 40 lb minimum. It does not apply USPS cubic prices, USPS ounce steps under 1 lb or any surcharge price. We did not test the rules by shipping a box with each carrier. Not confirmed: Canadian carriers, Priority Mail and other USPS services, and how any shipping platform applies these rules to its labels.