What this calculator does
This tool estimates the weight basis a carrier may use when a box is large for its actual scale weight. It does not calculate postage, delivery commitment, fuel surcharge, additional handling, residential surcharge, large-package minimum billable weight, hazardous-material fees, declared value, pickup fees, taxes, or contract pricing.
Rules implemented
| Carrier | Service and rate type | Dimension rounding | Divisor | DIM condition | Official basis |
|---|---|---|---|---|---|
| FedEx | U.S. and international package services; published Service Guide rule. | Service Guide rule applied; effective_from is NOT_VERIFIED for the dimension-rounding change. | 139 in3/lb | May apply to all shipments in customer packaging. | Verified against the 2026 FedEx Service Guide, updated June 1, 2026. FedEx Service Guide 2026 |
| UPS | Package services under Daily Rates. | Any fractional measurement rounds up to the next whole number. | 139 in3/lb | May apply to all UPS domestic and international package services. | UPS Daily Rate and Service Guide |
| UPS | Package services under Retail Rates, kept separate from Daily. | Uses the same public package measurement method; Retail is separated as a rate type. | 139 in3/lb | May apply to package services; final Retail rate table is separate. | UPS Retail Rates 2026 and UPS Terms |
| USPS | Priority Mail, Priority Mail Express, USPS Ground Advantage, and Parcel Select before 2026-07-12. | Round off each measurement to the nearest whole inch. | 166 in3/lb | Only when rounded volume exceeds 1,728 cubic inches. | USPS DMM 123 |
| USPS | Same competitive package products from 2026-07-12. | Round up each measurement to the nearest whole inch. | 139 in3/lb | Only when rounded volume exceeds 1,728 cubic inches. | Federal Register USPS 2026 change |
Use this with the box-size guides
After checking the estimate, review DIM vs actual vs billable weight, standard shipping box sizes, inner vs outer dimensions, and the shipping-weight rules methodology. For moving-specific planning, pair this with the Box Count Calculator, Storage Unit Estimator, and Moving Supply Database.