Free, no signup. Rules checked November 2026
USPS dimensional weight calculator
Enter a box size to see whether USPS DIM weight applies and what you'll be billed.
USPS only charges dimensional weight on boxes over one cubic foot, and on July 12, 2026 it changed the divisor from 166 to 139 and began rounding every dimension up. Enter your box and weight to see whether it crosses the 1,728 cubic inch line and what USPS will bill for Priority Mail, Ground Advantage and Parcel Select.
USPS dimensional weight rules since July 12, 2026
From the USPS final rule published May 15, 2026 and the Domestic Mail Manual.
| Divisor | 139. It was 166 until July 12, 2026. |
|---|---|
| Size trigger | Only parcels over 1 cubic foot (1,728 cubic inches). At or under that, you pay on scale weight. |
| Rounding dimensions | Each side rounds up to the next whole inch. Before July 12, 2026 USPS rounded to the nearest inch. |
| Services | Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select, at retail and commercial prices. |
| Exempt | Flat Rate boxes and envelopes, which are one price up to 70 lb. |
| Cap | If DIM weight comes out over 70 lb, you pay the 70 lb price. |
What the July 2026 change did to USPS bills
Two rules changed on the same day, and together they raised the billable weight of most large boxes.
166 became 139
A 16 × 14 × 12 inch box is 2,688 cubic inches. At 166 that was 17 lb. At 139 it is 20 lb.
Nearest inch became next inch
A side measuring 12.2 inches used to count as 12 and now counts as 13. That can push a box that was under one cubic foot over the line.
The one cubic foot rule stayed
A box at or under 1,728 cubic inches after rounding is still billed on scale weight alone. A 12 × 12 × 12 inch box is exactly at the line and stays exempt.
USPS now matches UPS and FedEx
All three use 139 and round up. The difference is that UPS and FedEx apply DIM weight to every box, and USPS only above one cubic foot.
USPS size limits and nonstandard fees
These are separate from dimensional weight and can apply to the same box.
Nonstandard length
A fee applies to parcels more than 22 inches long, and a higher one to parcels more than 30 inches long. Flat Rate packaging is not charged.
Nonstandard volume
A further fee applies to parcels over 2 cubic feet, which is 3,456 cubic inches.
Maximum size
Most services stop at 108 inches in length plus girth. Ground Advantage and Parcel Select go to 130 inches, at an oversized price above 108. Nothing can weigh more than 70 lb.
Tubes and odd shapes
For a parcel that is not rectangular, USPS multiplies the volume from its extreme dimensions by 0.785 before dividing by 139.
Three ways to stay out of USPS DIM weight
Because USPS has a size trigger, small changes to the box can remove the charge entirely.
Get under one cubic foot
Any combination that multiplies to 1,728 or less after rounding up is exempt: 12 × 12 × 12, 16 × 12 × 9, 18 × 12 × 8.
Use Flat Rate for heavy, bulky items
Flat Rate boxes ignore both weight and DIM weight up to 70 lb, so they suit dense or awkward items going a long way.
Ask about Cubic pricing
Commercial shippers can use Priority Mail Cubic for parcels up to half a cubic foot and 20 lb, and Ground Advantage Cubic up to one cubic foot. The price depends on size, not weight.
Measure the packed box
Every fraction rounds up, so a carton that bulges past a whole inch is billed at the next one.
USPS billable weight examples
Each row is what this calculator returns for that box under the rules in effect since July 12, 2026.
| Box | Billable weight | Why |
|---|---|---|
| 12×12×12 in, 3 lb 1,728 in³ | 3 lb (DIM not applied) | Exactly one cubic foot, so DIM weight does not apply. |
| 12.2×12×12 in, 3 lb 1,872 in³ | 14 lb | A fifth of an inch over rounds to 13 and crosses the line. |
| 16×14×12 in, 6 lb 2,688 in³ | 20 lb | Billed at 20 lb at 139. It was 17 lb at 166. |
| 18×12×8 in, 9 lb 1,728 in³ | 9 lb (DIM not applied) | Exactly 1,728 cubic inches, billed on scale weight. |
| 24×18×12 in, 10 lb 5,184 in³ | 38 lb | Over 22 inches long and over 2 cubic feet, so nonstandard fees apply too. |
How to calculate USPS dimensional weight
Three steps. The calculator above does all of them as you type.
Step 1
Measure and round up
Measure length, width and height and round each up to the next whole inch.
Step 2
Check the cubic inches
Multiply the three numbers. If the result is 1,728 or less, stop: you pay on scale weight.
Step 3
Divide by 139
If it is over 1,728, divide by 139 and round up. USPS bills the greater of that and the scale weight, up to the 70 lb price.
USPS dimensional weight FAQs
- What is the USPS DIM divisor?
- 139, since July 12, 2026. Before that date it was 166. USPS divides the parcel's cubic inches by 139 and rounds up to the next pound, but only for parcels over 1,728 cubic inches.
- When does USPS charge dimensional weight?
- Only when a parcel is over one cubic foot, which is 1,728 cubic inches, after rounding each side up to the next inch. It applies to Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select at both retail and commercial prices.
- Does USPS Ground Advantage use dimensional weight?
- Yes, for parcels over one cubic foot, at the 139 divisor. Ground Advantage parcels at or under 1,728 cubic inches are priced on scale weight.
- Do USPS Flat Rate boxes use dimensional weight?
- No. Flat Rate boxes and envelopes are one price to any US address for up to 70 lb, regardless of weight or DIM weight.
- Is a 12 × 12 × 12 box subject to USPS dimensional weight?
- No. It is exactly 1,728 cubic inches, and DIM weight applies only above that. If any side measures over 12 inches it rounds up to 13 and the box becomes subject to it.
- What is the maximum size for a USPS package?
- 70 lb, and 108 inches in combined length and girth for most services. USPS Ground Advantage and Parcel Select accept up to 130 inches, at an oversized price above 108.
- Is USPS billable weight lower than UPS or FedEx?
- At or under one cubic foot it can be. USPS bills the scale weight there, while UPS and FedEx bill the greater of scale weight and DIM weight, so a light box bills lower on USPS. Above one cubic foot all three divide by 139. Differences then come from size-surcharge minimums, the USPS 70 lb cap and the 166 divisor on UPS retail rates. See all carriers side by side.
Compare with other carriers
The same box can bill at a different weight depending on who carries it.
- All carriers side by sideUPS, FedEx and USPS billable weight for one box, in one table.
- FedEx Dimensional Weight CalculatorFedEx DIM and billable weight at ÷139 with 2026 round-up rules, plus Additional Handling and Oversize checks.
- UPS Dimensional Weight CalculatorUPS DIM and billable weight at ÷139 (daily) and ÷166 (retail), plus Additional Handling and Large Package checks.
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