US Postage Cost Calculator
USPS postage depends on the mail class, weight and any extra services, and the prices change periodically. This calculator estimates your total mailing cost from a base price for the first ounce, an additional-ounce charge for the rest of the weight, any extra-service fee, and the number of pieces. Because USPS prices change, the rate figures are editable inputs: enter the current values from the USPS Notice 123 price list and the calculator returns the per-piece and total cost.
Postage cost formula
Additional ounces = ceil(weight) - 1 (not below 0) Cost per piece = base price + (additional ounces x additional-ounce charge) + extra service fee Total = cost per piece x number of pieces
Weight is rounded up because USPS charges per ounce or part of an ounce. Check the maximum weight for your mail class.
Worked example
Base price 0.73, additional-ounce charge 0.28, weight 2 ounces, no extra service, 1 piece. Additional ounces = 1, so per piece = 0.73 + 0.28 = 1.01, total = 1.01.
US postage: frequently asked questions
How does USPS price first-class mail?
USPS first-class mail pricing has a base price that covers the first ounce (for letters) and an additional charge for each ounce above that, up to the weight limit for the class. Flats and packages use different price tables. Because USPS changes its prices periodically, this calculator takes the base price and per-ounce charge as editable inputs from the current USPS price list.
Why are the rates editable inputs?
The US Postal Service updates its prices through filings with the Postal Regulatory Commission, often more than once a year. To avoid showing a stale price, this calculator lets you enter the current base price, additional-ounce charge and any extra-service fee from the USPS Notice 123 price list, then multiplies by your weight and quantity.
What are additional ounces?
For first-class letters, the base price covers the first ounce. Each additional ounce (or part of an ounce) up to the maximum is charged at the additional-ounce rate. Enter the total weight in ounces; the calculator charges the base price for the first ounce and the per-ounce rate for the rest.
What counts as an extra service?
Extra services include Certified Mail, Registered Mail, return receipt, insurance, and signature confirmation, each with its own fee added on top of postage. If you are using one, enter its fee in the extra-service field and the calculator adds it to every piece.
Official sources
- United States Postal Service: Notice 123 Price List.
- United States Postal Service: USPS Prices.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.