Stamp Quantity Calculator
Enter the weight and the stamp you have on hand, and see exactly how many to stick on — plus the little leftover value — so a young letter-writer never guesses at the mailbox.
No more guessing at stamps
Under-stamp a letter and it comes back; over-stamp it and you waste a stamp. This calculator takes the worry out by turning the letter’s weight into the exact postage due, then rounding up to the whole stamps that cover it. It’s a small, real bit of arithmetic kids can own — and a great way to use up a jar of odd-value stamps.
Not sure of the postage itself? Start with the Postage Calculator, and match the envelope with the Envelope & Paper Size Matcher.
Frequently Asked Questions
How many stamps does my letter need?
It depends on weight. A one-ounce letter needs a single first-class (Forever) stamp; each extra ounce adds a little more postage, which may push you to a second stamp. Enter the weight and the value of the stamp you have, and the calculator rounds up to the number of whole stamps that covers the postage due.
Can I use several small stamps instead of one big one?
Absolutely — that's how most stamp collections get used up. As long as the stamps' values add up to at least the postage due, the letter goes. The calculator shows the total value you'd apply and the small overage, so you can see when a couple of low-value stamps together will do the job.
What is a Forever stamp?
A Forever stamp always covers a standard one-ounce first-class letter, no matter when you bought it or how rates change. That makes it the simplest stamp for kids: one Forever stamp equals one normal letter. For heavier letters you simply add more postage on top.
Why is there an 'overage'?
Because you can only stick on whole stamps, the value applied is often a few cents more than the exact postage — that difference is the overage. It's harmless; the post office simply doesn't give change. To trim it, mix a smaller-value stamp in rather than adding a second full-price one.
Uses curated illustrative first-class letter rates and rounds up to whole stamps. Confirm the live postage at the counter before mailing anything important.