Two Stamps Cover More Than You Think
Stamps come in fixed values and postage does not, so the two almost never meet exactly. What you actually pay is the stamps rounded up, and the gap between those two numbers is money that simply disappears.
The stamp calculator reports that gap as the overage, and reading it across a few weights turns up something genuinely useful.
What a Forever stamp covers
| Letter weight | Postage due | Stamps at $0.82 | You pay | Wasted |
|---|---|---|---|---|
| 1 oz | $0.82 | 1 | $0.82 | none |
| 2 oz | $1.11 | 2 | $1.64 | $0.53 |
| 3 oz | $1.40 | 2 | $1.64 | $0.24 |
| 3.5 oz | $1.69 | 3 | $2.46 | $0.77 |
The prices in this post are USPS retail prices effective July 12, 2026, and a Forever stamp is worth the current one-ounce letter price, $0.82, whenever you bought it. Check the current rate before you post: prices usually change each January and July.
The free ounce hiding in the middle
Look at the 2 oz and 3 oz rows. Both need 2 stamps. Both cost you $1.64.
At 2 oz you are throwing away 53¢. At 3 oz you are throwing away 24¢. The extra ounce of paper — six or seven more sheets — costs nothing at all, because you had already bought it the moment you reached for the second stamp.
So if a letter has crept past one ounce and you are putting a second stamp on it anyway, you have room for a great deal more than you think. Use it.
Where it turns bad
At 3.5 oz the postage due is $1.69, which needs 3 stamps worth $2.46. The overage jumps to 77¢ — 94% of a whole stamp, gone.
That is the worst-value weight on the whole scale. Going from 3 oz to 3.5 oz adds half an ounce of paper and costs an entire extra stamp. If you are at 3 oz, either stay there or accept that the next half-ounce is the most expensive paper you will ever post.
The stamp nobody buys
Postage does not have to be all Forever stamps. Any mix of stamps that adds up to the postage due is fine, and each ounce after the first costs $0.29 on a letter. Stamps in smaller values close this gap, and almost nobody at a counter asks for them.
A 3 oz letter paid entirely in stamps worth $0.29 takes 5 of them, costs $1.45, and wastes only 5¢ against 24¢ the Forever way. The realistic version is one Forever stamp for the first ounce and smaller stamps for the rest: $0.82 plus two stamps worth $0.29 is exactly $1.40, with nothing wasted.
It also looks better. 3 identical Forever stamps crowded into a corner is the visual signature of someone guessing.
Why "Forever" is still the right default
A Forever stamp is valid for one ounce of domestic letter mail whatever the rate becomes later. Buy a book today and it still posts a letter after the next price rise, which makes it a small hedge as well as a stamp.
The overage is the price of that convenience, and for a single birthday card it is not worth a second thought. It becomes worth thinking about when a child is writing weekly: 53¢ a week is about $27.56 a year in stamps that did nothing.
What the calculator is really telling you
Put your letter's weight in and the useful output is not the stamp count — you would have worked that out. It is the overage. A big overage means you are just past a boundary, and being just past a boundary is always a choice you can revisit.
Overage near zero: your weight and your stamps agree. Nothing to do.
Overage around 53¢: you have bought an ounce you are not using. Add pages.
Overage over 60¢: you have crossed a boundary for the sake of a very small amount of paper. Take something out, or switch to additional-ounce stamps.
One last thing children get wrong
More stamps do not make a letter arrive faster. They make it arrive, which is a lower bar than it sounds, and anything beyond the postage due is simply a gift to the postal service.
Speed is bought with the class of service, not with decoration. Three stamps on a standard letter buys exactly the same journey as one correct stamp — just at three times the price.
What happens when the rates change
Postal rates change often, and when they do the overage table above shifts. What does not shift is the shape: stamps are coarse, postage is fine, and rounding up always costs something.
The one number worth re-checking after a rise is whether your usual letter still fits one stamp. A Forever stamp always covers the first ounce, because it is worth the current one-ounce price on the day you post it. The additional-ounce rate is what moves the count, and a letter that needed two stamps last year may need three this year without changing at all.
A book of stamps is a household object
The single change that makes a child write more letters is having stamps in the house. A letter written on a Sunday afternoon and posted on Monday morning gets sent; one that requires a trip to a counter first usually does not.
A book of twenty Forever stamps and a strip of additional-ounce stamps in the same drawer as the envelopes covers almost every letter a child will write in a year, at a total cost of about $19.30. Keep them somewhere a child can reach without asking, which is the part that actually matters.
Then the calculator becomes a ten-second check rather than a shopping list: weigh, read the stamp count, take that many out of the drawer, and go.
What the overage is really measuring
It is not waste in any moral sense. It is the price of a system where postage is precise and stamps are not, and a few cents on a birthday card is a completely reasonable thing to lose.
What it is useful for is as a signal. A large overage always means the same thing: you are sitting just past a boundary, and boundaries are the only places in postal pricing where a small change to the envelope makes a large change to the price.
So read it as a question rather than a cost. 77¢ of overage is the tool asking whether that last half-ounce was worth an entire stamp — and sometimes the honest answer is yes, because the thing inside matters more than the arithmetic does.