USPS Dimensional Weight Calculator
Check whether the size of a rectangular Priority Mail parcel changes its billable weight. Enter the box measurements and actual weight to see the volume, dimensional-weight test and resulting weight used for planning.
Package calculation breakdown
| Measure | Box A | Box B |
|---|
A smaller box can lower billable weight without guaranteeing a lower price. Nonstandard fees are not calculated. A dimensional weight above 70 lb uses the 70 lb price only when actual weight and size remain within their limits.
How to use this tool
- Select the supported service and packaging.
- Measure the package at its widest points.
- Compare the result with a smaller suitable box if available.
How the result is calculated
The supported USPS rule compares actual weight with dimensional weight when the rounded package volume exceeds the specified threshold. Dimensional weight is rounded up after division by the service's divisor.
Worked example
A 20 by 15 by 10 inch box has a volume of 3,000 cubic inches. With a divisor of 166, its dimensional weight rounds up to 19 pounds.
What this result does not cover
Billable weight is not a postage quote. Destination, service, packaging, surcharges and eligibility still affect the final price.
Questions people ask
Does this apply to Flat Rate boxes?
No. The initial calculator excludes Flat Rate packaging.
Can I use centimetres?
Convert to inches first or use the unit switch before carrier rounding is applied.
Will a smaller box always cost less?
It can reduce dimensional weight, but the final price also depends on the service and destination.
Current rule clarification
The document example above uses the historical divisor of 166. The rule effective July 12, 2026 rounds dimensions upward and uses divisor 139; the same box has a dimensional weight of 22 pounds. Select the applicable rule period. This version accepts inches; convert centimetres to inches by dividing by 2.54 before entering dimensions.
Sources and rule dates
- USPS DMM 123 — Priority Mail prices and eligibility: current dimensional-weight rule effective July 12, 2026.
- USPS DMM 101 — physical standards: size and actual-weight limits.
- USPS Quick Service Guide 120: overview; its 166-divisor examples reflect the earlier rule.
- USPS rule revision effective June 23, 2019: historical divisor 166.
Rule owner: Toolistify. Sources last retrieved and reviewed October 20, 2026; retrieval date is separate from each rule's effective date. Recheck each USPS price or DMM revision; next scheduled check January 1, 2027. Later changes are not automatically loaded.
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