Postage Calculator

A postage calculator helps you estimate how much it costs to mail a letter, postcard, large envelope, or package using the United States Postal Service (USPS). Instead of guessing at the post office counter or paying for the wrong service, you can enter your mail's type, weight, and destination to instantly see the estimated cost before you go.

USPS uses a tiered pricing system based on several variables: the mail piece type (postcard, letter, large envelope, or package), the weight in ounces, and whether the destination is domestic (within the USA) or international. Each combination maps to a specific service class with its own rate structure and delivery window.

This calculator covers the four main First-Class and Ground mail categories and also displays comparison costs for Priority Mail (1–3 business days) and Priority Mail Express (1–2 business days), so you can make an informed decision about speed versus cost at a glance. Rates shown are estimates based on 2024 USPS pricing; always confirm the final rate at usps.com before mailing.

Whether you are sending birthday cards, business invoices, or online-store shipments, knowing the postage cost upfront helps you budget correctly, choose the right service, and avoid delays caused by insufficient postage.

The USPS calculates postage using a combination of mail piece classification, weight, and destination. Each mail type has its own rate schedule that steps up as weight increases.

Domestic Letter Rates (First-Class Mail)

Standard letters are priced in 1-ounce increments up to the 3.5-ounce maximum:

Domestic Large Envelope (Flat) Rates

Large envelopes start at $1.50 for the first ounce, then add $0.24 per additional ounce above 4 oz:

Postcards have a flat domestic rate of $0.53 and an international rate of $1.55.

Packages follow a different pricing model based on weight in pounds rather than ounces. The calculator converts your ounce entry to pounds (lbs = oz ÷ 16) before applying the rate schedule.

For domestic USPS Ground Advantage packages:

• If the package weighs 1 lb or less: postageCost = $5.00 + (oz × $0.15)
• If the package weighs more than 1 lb: postageCost = $7.00 + (lbs × $1.50)

For international packages (First-Class Package International):

• postageCost = $15.00 + (lbs × $3.00)

The calculator also always shows two upgrade options regardless of mail type:

• Priority Mail (domestic): $8.50 + (oz ÷ 16 × $2.00)
• Priority Mail (international): $30.00 + (oz ÷ 16 × $5.00)
• Priority Mail Express (domestic): $28.00 + (oz ÷ 16 × $3.00)
• Priority Mail Express (international): $50.00 + (oz ÷ 16 × $8.00)

These upgrade costs are computed in parallel so you can immediately compare the price difference for faster delivery. For heavy or time-sensitive parcels, Priority Mail Express offers the fastest guaranteed service USPS provides.

Keep in mind that USPS Ground Advantage has a maximum weight of 70 lbs (1,120 oz) and a combined length plus girth limit of 130 inches. Items exceeding these limits must be shipped via a freight carrier.

Sending mail internationally adds cost and transit time. The USPS offers First-Class Mail International for lightweight letters and envelopes, and First-Class Package International for small parcels. Rates differ significantly from domestic pricing.

International letter rates:

• Up to 1 oz: $1.55
• Up to 2 oz: $2.30
• Over 2 oz: $2.30 + ((oz − 2) × $0.75)

International large envelope rates:

• postageCost = $3.50 + (oz × $0.50)

International delivery typically takes 7–21 business days, depending on the destination country's customs processing. Factors like local holidays, customs inspection backlogs, and remote delivery areas can extend transit times beyond the estimate. For important or time-sensitive international shipments, upgrading to Priority Mail International or Priority Mail Express International provides faster service with tracking included.

Note that some countries have import restrictions on certain goods, and your package may be subject to customs duties paid by the recipient. Always check the destination country's regulations before mailing goods internationally.

A few simple habits can meaningfully reduce your annual mailing costs, especially if you send high volumes of mail for a business or regular correspondence.

Use Click-N-Ship: Purchasing postage online at usps.com through Click-N-Ship or similar services often saves money compared to paying retail rates at the counter. USPS Commercial rates are available to any shipper who prints postage online.

Choose the right mail class: Upgrading to Priority Mail is only worth it when speed genuinely matters. For non-urgent correspondence, First-Class Mail or USPS Ground Advantage almost always provides acceptable delivery times at a lower cost.

Weigh before you seal: Adding even a single sheet of paper to a letter can push it over the 1-ounce threshold and add $0.24 to your cost. Use a kitchen or postal scale at home to weigh items before mailing.

Use flat-rate boxes strategically: For heavy items that fit in a flat-rate Priority Mail box, the flat rate may be cheaper than weight-based pricing. The breakeven point depends on how heavy your package is and the distance it needs to travel.

Maintain proper dimensions: Mail pieces that fall outside USPS size standards are assessed a non-machinable surcharge of around $0.40. Keep letters within 11.5" × 6.125" × 0.25" to avoid this extra fee.

Use postcards instead of letters when appropriate: At $0.53 domestic versus $0.68 for a letter, postcards save $0.15 per piece. For bulk marketing mailings this difference adds up quickly.