USPS Dimensional Weight Calculator
Current USPS commercial-parcel guidance applies dimensional-weight steps to listed services when a rectangular parcel exceeds one cubic foot, then divides cubic inches by 166 and rounds up.
USPS divisor 166 and the volume threshold
The USPS January 18, 2026 commercial parcel quick-service guide covers Priority Mail Express, Priority Mail, USPS Ground Advantage Commercial, and Parcel Select Destination Entry. For its rectangular-parcel example, dimensions are rounded as directed and dimensional weight applies when volume is more than 1,728 cubic inches.
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.
Official USPS reference
Consult the USPS commercial parcels quick-service guide dated January 18, 2026 and the current Domestic Mail Manual before purchasing postage.
Frequently asked questions
What USPS DIM divisor is shown in current guidance?
The referenced January 2026 USPS commercial-parcel guide uses divisor 166 for applicable parcels.
When does the USPS example apply dimensional weight?
Its rectangular-parcel instructions apply the DIM calculation when volume is more than 1,728 cubic inches for the listed services.
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.