USPS Dimensional Weight Calculator
The current USPS Domestic Mail Manual applies dimensional-weight pricing to specified parcels over one cubic foot, using divisor 139 and rounding up under the applicable service rules.
USPS divisor 139 and the volume threshold
Current USPS Domestic Mail Manual sections for Priority Mail, Priority Mail Express, USPS Ground Advantage, and Parcel Select use dimensional-weight rules for applicable parcels exceeding 1,728 cubic inches. For rectangular parcels, dimensions are rounded up to whole inches, cubic volume is divided by 139, and the result is rounded up to the next whole pound.
The calculator can show the raw DIM result, but you must apply the current USPS eligibility, threshold, shape, and rounding requirements for the mail class.
Nonrectangular parcels need special handling
USPS documentation provides separate steps for nonrectangular parcels, including an adjustment factor in applicable rules. A simple rectangular-box calculation should not be treated as the final result for every parcel shape or service.
Check the one-cubic-foot threshold first
A 12 × 12 × 12 inch rectangular parcel is exactly 1,728 in³, while a 13 × 12 × 12 inch parcel is 1,872 in³. For a cited USPS service where the dimensional-weight rule applies above one cubic foot, the second parcel crosses the volume threshold and produces 13.47 lb before the DMM’s applicable rounding. This threshold check comes before treating a generic DIM result as USPS billable weight.
Official USPS reference
Consult the current USPS Domestic Mail Manual sections for Priority Mail Express, Priority Mail, Ground Advantage Retail, Ground Advantage Commercial, and Parcel Select before purchasing postage.
Frequently asked questions
What USPS DIM divisor is shown in the current DMM?
Current USPS DMM sections use divisor 139 for applicable rectangular parcels exceeding one cubic foot.
When does USPS apply dimensional weight?
The cited DMM sections apply dimensional-weight pricing to specified parcels exceeding 1,728 cubic inches, subject to service and destination rules.
How are nonrectangular USPS parcels calculated?
USPS publishes separate rules for nonrectangular shapes, so use the current Domestic Mail Manual rather than a basic box formula alone.