USPS Rate Calculator
USPS postage depends on the package weight, dimensional size, destination zone, and service level. This calculator translates those forces into a single estimate by combining the service base, volumetric weight, applicable zone multiplier, and any residential surcharge.
The calculator applies volumetric weight (length × width × height ÷ 166), respects the highest edge for dimension-based adjustments, and scales the sum by a zone factor so longer distances cost more. Respectively, base prices start with Priority Mail, First-Class Package, Retail Ground, and Priority Mail Express tiers before multipliers adjust for weight and zone.
Example: a 5 lb parcel measuring 14″ × 10″ × 4″ traveling from zone 4 to zone 7 via Priority Mail uses a volumetric weight of about 3.37 lbs and a zone multiplier of 1.30; the recalculated postage lands near $17.20, matching typical USPS behavior for similar packages.
- Volumetric weight ensures light-but-bulky parcels pay their fair share.
- Zone multipliers rise by 0.05 per zone step, mirroring longer distances.
- The final cost includes a $3.25 residential delivery surcharge when selected.