How much does a postage stamp cost? A Forever stamp runs $0.78as of January 2026 — but that number alone is why so many people overpay. The instinct is to slap two stamps on anything heavier than a single sheet and drop it in the mailbox. On a 2 oz letter, that habit wastes $0.50 every time. Send 50 holiday cards that way and you've handed USPS $25 it never asked for. The calculator above fixes that: tell it what you're mailing and it shows the exact stamp combination, not a rounded-up guess.
The "Two Forever Stamps Covers It" Myth
Here's the belief that costs people money: when in doubt, use two Forever stamps.Two stamps is $1.56 of postage. A standard letter never needs that until it's past 3.5 oz — and at 3.5 oz it's actually reclassified as a large envelope anyway. For everything in between, the exact rate is lower, and USPS sells the specific stamps to hit it. A 2 oz letter needs one Forever stamp plus one $0.28 additional-ounce stamp, totaling $1.06. Use two Forevers and you've overpaid by exactly $0.50.
The fix isn't complicated. Forever stamps are designed to cover the first ounce of First-Class mail forever, no matter how rates climb. Additional-ounce stamps, postcard stamps, and Global Forever stamps fill the gaps. Keep a small mix on hand and you stop rounding up. The calculator's "if you only have Forever stamps" panel shows you precisely what the lazy approach costs on your specific piece of mail.
What Each Stamp Actually Costs in 2026
USPS adjusts prices most years in January and July. The January 2026 schedule below is what the calculator runs on. These are the stamps you'll actually buy at the counter or on a roll — not mail-class rates, but the physical denominations.
| Stamp | 2026 Price | What it covers |
|---|---|---|
| Forever stamp | $0.78 | First ounce of a domestic First-Class letter |
| Additional-ounce stamp | $0.28 | Each extra ounce on a letter, up to 3.5 oz |
| Postcard stamp | $0.58 | One standard-size postcard |
| Non-machinable surcharge | $0.46 | Added to square, rigid, or lumpy letters |
| Global Forever stamp | $1.65 | A 1 oz letter to any country worldwide |
Notice the postcard stamp at $0.58. Drop a Forever stamp on a postcard and you've overpaid $0.20 — small, but it adds up across a vacation's worth of cards. For full mail-class pricing (Priority, Ground Advantage, flat-rate boxes), our USPS postage calculator goes deeper into rates by service.
How Many Stamps Do I Need? (The Real Math)
The number of stamps depends on weight and shape, not how the envelope feels in your hand. A letter is charged in whole ounces: the first ounce is the Forever stamp, then $0.28 for each ounce after. Here's the breakdown the calculator uses for a standard domestic letter, with the cheapest exact combination versus the Forever-only habit.
| Letter weight | Exact stamps | Exact cost | Forever-only |
|---|---|---|---|
| 1 oz (3–4 sheets) | 1 Forever | $0.78 | 1 stamp — exact |
| 2 oz (8–10 sheets) | 1 Forever + 1 add'l oz | $1.06 | 2 stamps ($1.56) — +$0.50 |
| 3 oz (14–15 sheets) | 1 Forever + 2 add'l oz | $1.34 | 2 stamps ($1.56) — +$0.22 |
| 3.5 oz (letter max) | 1 Forever + 3 add'l oz | $1.62 | 3 stamps ($2.34) — +$0.72 |
Past 3.5 oz, a letter becomes a large envelope ("flat") starting at $1.50 for the first ounce. That $0.78-to-$1.50 jump at the 3.5 oz line is the single biggest reason to weigh mail before you stamp it. Half an ounce of extra paper can nearly double your postage. If you mail packages rather than letters, compare carriers first with our shipping cost calculator.
Mistakes That Quietly Cost You Money
Most postage waste comes from a handful of repeat offenders. Each one has a dollar figure attached:
- The square greeting card.Square envelopes can't run through automated sorters, so they carry the $0.46 non-machinable surcharge. A 1 oz square card costs $1.24, not $0.78. Around the holidays this catches thousands of senders off guard — on a box of 30 wedding invitations, that's $13.80 in surcharges nobody budgeted for.
- The lumpy letter. Slip a key, a USB drive, or a thick gift card into a regular envelope and it becomes non-machinable too. Same $0.46 penalty, or worse if it gets bumped to package rates.
- Rounding postcards up. A postcard needs a $0.58 stamp. Using a Forever stamp works but burns an extra $0.20 per card.
- Underpaying.Too few stamps and mail with a return address comes back to you; without one, the recipient gets a "Postage Due" slip. Either way it's delayed days. The calculator's exact combo keeps you from guessing low.
When Stamps Aren't the Right Move
Stamps win for letters, cards, and the occasional postcard. They stop making sense the moment you're shipping a package. Anything over 3.5 oz that isn't a flat envelope — a small box, a padded mailer with a bump in it — should go by Ground Advantage or Priority Mail, where buying postage online through USPS Click-N-Ship gets you Commercial rates 5–15% below the stamp-counter price. Stamps also can't add tracking or insurance; a printed label can. If you're mailing the same thing in volume every week, a $0.78 stamp on each piece is the most expensive way to do it.
One genuinely useful stamp trick: because Forever stamps hold their value through rate hikes, buying a roll right before an announced increase locks in the lower price. USPS posts changes about 45 days ahead through the Postal Regulatory Commission. A roll of 100 bought at $0.73 before the last bump still mails a 1 oz letter today, even though the rate is now $0.78 — a built-in $5 hedge per roll.