Disclaimer
Please read this disclaimer carefully. It explains what our stamp and postage tools can—and cannot—do.
Estimates only
All amounts, stamp counts, and suggestions shown by Stamp Calculator are estimates based on commonly published USPS guidelines for domestic First-Class letter mail and related surcharges we choose to model. They are meant to help you plan and learn, not to replace official USPS guidance for your exact piece of mail.
Actual postage depends on exact weight, dimensions, thickness, shape, contents, classification (letter vs. large envelope vs. package), and current USPS prices. Clerks and automated equipment may interpret borderline items differently than your kitchen scale or ruler.
Verify with official sources
You should verify results with official USPS sources before mailing anything important. Use usps.com, retail postage price lists, self-service kiosks, or a post office when you need certainty. Rates and rules change; our site may not reflect the very latest notice the day it goes live everywhere.
No guarantee of accuracy
We make reasonable efforts to keep logic and numbers aligned with general public information, but we offer no warranty or guarantee of accuracy, completeness, or fitness for a particular purpose. If an estimate is wrong for your situation, we are not responsible for extra postage, returned mail, delays, or other costs.
Not affiliated with USPS
Stamp Calculator is an independent educational website. We are not affiliated with the United States Postal Service, not endorsed by USPS, and not a substitute for USPS tools or employees. For authoritative decisions about postage and mailability, rely on USPS.
What this tool does not cover
Our calculators focus on scenarios we describe on each page—typically domestic First-Class letter-style mail with the inputs we support. They do not replace professional advice for registered mail, insurance, customs, international letters, flats and packages priced under different charts, or commercial presort. If your mailing falls outside those cases, use USPS resources or a qualified mail professional.
Using this site does not create a contract, client relationship, or duty of care between you and the site operators. You remain solely responsible for compliance with postal regulations and for the postage you affix before depositing mail with the Postal Service or another carrier.
Related policies
For how we handle data and site rules, see our Privacy Policy and Terms of Service.