About Invitation Postage
Invitation Postage is a free calculator for one question: how much postage does this invitation need? It exists because the answer is surprisingly hard to get. Forum threads quote old prices, and two post office clerks can give two different answers for the same square envelope.
Where the numbers come from
Every price on this site is read from the USPS price list, Notice 123. Every rule is read from the USPS Domestic Mail Manual, mainlysection 101 on physical standards, and fromPublication 25. Nothing is taken from memory or from other websites.
The rates were last verified on October 9, 2026, against the price list that took effect on October 4, 2026. That date appears in the footer of every page and on every result.
How the calculator works
You enter the envelope size, weight, thickness and anything attached. The calculator applies the same tests a postal clerk would: size limits, the aspect ratio rule, the list of nonmachinable features, and the weight steps. It then shows the mail class, the price, and the specific rule behind the answer, with a link to the USPS text.
All of that happens in your browser. Nothing you type is sent anywhere.
What it does not do
- It does not price packages. If your piece would ship as a package, it says so and points you to USPS.
- It covers mail within the United States only.
- It cannot bend your envelope for you. Whether something is too rigid is a judgment a clerk makes by hand.
For anything unusual, take one finished, sealed invitation to a post office counter before you buy stamps for the whole batch.
Not a USPS site
Invitation Postage is an independent site. It is not affiliated with, endorsed by, or operated by the United States Postal Service.