Short answer: carriers bill the greater of actual pounds or dimensional weight. Enter your box, see USPS Ground Advantage vs UPS Ground vs FedEx Ground side by side, then decide whether rate-shopping software is worth it. Also see USPS vs UPS vs FedEx.
This tool estimates billable weight using currently published DIM divisors and rounding rules as of publication (updated for USPS's July 12, 2026 divisor change). It is a planning estimate, not a live carrier quote — always confirm actual rates with your carrier or shipping platform before pricing a shipment.
Billable weight = the greater of actual weight or dimensional weight (each dimension rounded up to the next inch, then L×W×H ÷ divisor, rounded up). USPS only applies dimensional pricing to packages exceeding 1,728 cubic inches (1 cubic foot); below that threshold, USPS bills actual weight. Divisors and thresholds can change — verify current figures with each carrier.
Same rules the calculator uses (divisor 139; USPS applies DIM only above 1,728 in³). No dollar rates — billable pounds only. Plug each into the tool above to reproduce.
Input: 2 lb actual · 12×10×8 in (960 in³, under 1 cubic foot).
Takeaway: a light shirt in a roomy box often pays UPS/FedEx as if it were heavier. Shrink the box or stay on USPS for this profile.
Input: 20 lb actual · 10×8×6 in (480 in³).
Takeaway: dense goods rarely trip dimensional pricing. Compare carriers on zone, speed, and surcharges — not on DIM math.
Input: 4 lb actual · 20×16×12 in (3,840 in³, above USPS threshold).
Takeaway: oversized empty space is expensive on every major ground network. Cut the carton or fill denser before you shop rates.
Once you know billable weight, software that quotes USPS, UPS, and FedEx on the same label can save more than tweaking one carrier. Partner links are not live yet — start with our shipping software comparison overview (affiliate slots coming soon), or keep using this calculator for package planning.
For each carrier, we round each dimension up to the next whole inch, then calculate dimensional weight as (Length × Width × Height) ÷ DIM divisor, rounded up to the nearest pound. We then compare that figure to your package's actual weight and report whichever is higher — that's your billable weight. USPS only applies this calculation to packages over 1,728 cubic inches; smaller packages are billed at actual weight. See the full explanation, including USPS's July 2026 divisor change, in our guide on how dimensional weight pricing works, or see the structural differences between carriers in our carrier rate comparison table. If you ship often enough to want multi-carrier quotes in one workflow, see our shipping software comparison (partner links coming soon) and the overview of shipping rate calculator tools.