Usps Postage Calculator

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USPS Postage Calculator
First-Class Mail® Postcard ($0.53)First-Class Mail® Letter (Standard Size)First-Class Mail® Large Envelope (Flat)USPS Ground Advantage™ (Small Package)
Estimated Total Postage:
$0.00
function calculatePostage(){var type=document.getElementById('mail_type').value;var weight=parseFloat(document.getElementById('weight').value);var qty=parseFloat(document.getElementById('quantity').value);var showBreakdown=document.getElementById('show_breakdown').checked;if(isNaN(weight)||weight<=0||isNaN(qty)||qty3.5){alert('Standard letters cannot exceed 3.5 oz. Calculated as Large Envelope/Flat instead.');unitPrice=1.39+Math.ceil(weight-1)*0.24;}else{unitPrice=0.68+(Math.ceil(weight-1)*0.24);}details="Letter: $0.68 base + $0.24/extra oz";}else if(type==='flat'){if(weight>13){alert('First-Class Flats cannot exceed 13 oz. Calculated using Ground Advantage rates.');unitPrice=5.40+(Math.ceil(weight-1)*0.15);}else{unitPrice=1.39+(Math.ceil(weight-1)*0.24);}details="Flat: $1.39 base + $0.24/extra oz";}else if(type==='ground'){unitPrice=5.40+(Math.ceil(weight-1)*0.15);details="Ground Advantage: Est. base $5.40 + $0.15/oz";}var total=unitPrice*qty;document.getElementById('totalCost').innerHTML=total.toFixed(2);if(showBreakdown){document.getElementById('breakdownText').innerHTML="Price per item: $"+unitPrice.toFixed(2)+" ("+details+")";}else{document.getElementById('breakdownText').innerHTML="";}}

How to Use the USPS Postage Calculator

The usps postage calculator is designed to help you estimate the cost of mailing items via the United States Postal Service. By entering the weight of your item and selecting the correct mail class, you can determine how many Forever stamps or how much metered postage you need before visiting the post office.

This tool is especially useful for small business owners, wedding planners sending invitations, or anyone sending personal correspondence who wants to avoid "Return to Sender" notifications due to insufficient postage.

Mail Type
Choose from Postcard, Standard Letter, Large Envelope (Flats), or Ground Advantage packages. Each has different size limits and pricing structures.
Weight (Ounces)
Enter the total weight of the item including the envelope and all contents. USPS rounds up to the nearest ounce (e.g., 1.2 oz is billed at the 2 oz rate).
Quantity
If you are mailing a batch of identical items, enter the number here to see the total budget required for your mailing project.

How Postage is Calculated

When using the usps postage calculator, the math varies based on the shape and weight of your mailpiece. The USPS uses a "base rate" for the first ounce and an "additional ounce" fee for everything after that. The formula used for standard letters is:

Postage = Base Rate + ((Total Ounces – 1) × Additional Ounce Rate)

  • Base Rate: The cost for the first ounce (currently $0.68 for letters).
  • Rounding: If your item weighs 2.1 ounces, the USPS charges for 3 ounces.
  • Weight Limits: Letters cannot exceed 3.5 ounces; once they do, they are reclassified as "Flats."
  • Shape Matters: Items that are rigid, square, or lumpy may incur a "non-machinable" surcharge.

Calculation Examples

Example 1: A Standard Wedding Invitation

Many wedding invitations weigh more than a standard 1-ounce letter due to thick cardstock and RSVP inserts. Let's assume an invitation weighs 2.3 ounces.

  1. Mail Type: First-Class Letter
  2. Weight: 2.3 oz (rounded up to 3 oz)
  3. Base Rate (1st oz): $0.68
  4. Additional 2 oz: 2 × $0.24 = $0.48
  5. Total Postage: $1.16

Example 2: A Large Flat Catalog

If you are mailing a 5-ounce catalog in a 9×12 envelope:

  1. Mail Type: First-Class Flat
  2. Weight: 5 oz
  3. Base Rate (1st oz): $1.39
  4. Additional 4 oz: 4 × $0.24 = $0.96
  5. Total Postage: $2.35

Common USPS Questions

What is a Forever Stamp?

A Forever stamp is always valid for the current First-Class Mail 1-ounce letter rate, regardless of when you purchased it. If you bought a Forever stamp at $0.60 and the price rises to $0.68, the stamp still covers the full 1-ounce postage without needing extra cents.

Does the usps postage calculator include tracking?

Standard First-Class letters and flats do not include tracking. To get a tracking number, you must upgrade to "USPS Ground Advantage" or "Priority Mail." Our calculator provides a Ground Advantage estimate for items that require tracking or exceed weight limits for letters.

When do postage prices change?

The USPS typically reviews and adjusts rates twice a year, usually in January and July. It is always best to check the latest rates using this tool before a large mailing to ensure your postage is up to date.

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