How many stamps do I need, it depends on how much the letter weighs

One 82 cent Forever stamp covers a standard letter up to 1 ounce. Past that, the honest answer to how many stamps do I need is whatever the scale says, because the Postal Service prices letters by the ounce, not by the envelope.

The price went up from 78 cents on July 12, 2026, and the 29 cent charge for each added ounce didn't move. A 4 cent bump sounds tiny until you're addressing a stack of holiday cards. Weigh first, then count stamps.

How many stamps do I need for a regular letter?

A regular letter is a paper, rectangular envelope no bigger than 11.5 by 6.125 inches and no thicker than a quarter inch, weighing 3.5 ounces at most. The table uses the official USPS Notice 123 price list to show how much postage for a letter you'll owe at each weight step, and the fewest Forever stamps that cover it.

Forever stamps alone overpay on heavier mail. A 2 ounce letter owes $1.11, but two Forever stamps add up to $1.64. Pair one Forever stamp with a 29 cent additional-ounce stamp and you land on $1.11 exactly. So for how many stamps for a letter between 1 and 3.5 ounces, think one Forever stamp plus one extra-ounce stamp for every ounce, or part of one, past the first.

Rule of thumb: one Forever stamp for the first ounce, then one 29 cent stamp for each additional ounce, up to 3.5 ounces. Heavier than that and it isn't a letter anymore.

How much does a letter weigh once it's stuffed?

Most people guess, and most guesses run light. Envelope paper is usually rated 20 to 24 lb, which Epson's paper specs list as 75 to 90 grams per square meter. A US letter sheet measures about 0.06 square meters, so a sheet of 20 lb copy paper weighs roughly 4.5 grams and a 24 lb sheet about 5.4 grams.

Sheets of paper per ounce

The envelope counts too, and so does anything tucked inside. Envelopes vary enough that weighing yours beats trusting a chart, so put an empty one on a scale once and remember the number. If you're not sure what a few grams feel like, our list of things that weigh a gram gives you everyday reference points.

Cards, photos and gift cards add up

Greeting cards are the usual surprise. A folded card with a photo, a ribbon or a gift card inside can creep past 28 grams without looking thick. Weigh one finished card before you stamp the whole batch, and run the reading through our grams to ounces converter if your scale only shows metric.

Five sheets of standard copy paper in a plain envelope is about the most one Forever stamp will carry. At six sheets, nearly any envelope tips the total over 1 ounce.

How many stamps for a large envelope, from 1 to 13 ounces

A large envelope, which the Postal Service calls a flat, is anything bigger than letter size, like the full-page mailers people use for documents they'd rather not fold. Flats start at $1.69 for the first ounce and climb 29 to 31 cents per ounce up to a 13 ounce maximum.

So how many stamps for a large envelope? Three Forever stamps cover anything up to 3 ounces, which handles most paperwork. Notice that a 1 ounce flat costs $1.69 while a 1 ounce letter costs $0.82, so folding four pages into a standard envelope cuts the postage by 87 cents.

When a flat becomes a package

Large envelopes have to be flexible, rectangular and evenly thick. The Postal Service charges package prices for a flat that's rigid or lumpy, and nothing over 13 ounces goes as a First-Class flat. For boxes and bulky mailers, our dimensional weight guide explains how size can outweigh the scale.

Square cards and lumpy envelopes need an extra 49 cents

Shape matters as much as weight. The Postal Service adds a $0.49 nonmachinable surcharge to letters its sorting machines can't handle, which brings a 1 ounce square card to $1.31. Two Forever stamps cover it. One won't.

The surcharge applies even when the letter is featherlight. A square invitation at half an ounce still owes $1.31, so check the envelope shape before you buy invitation stock, not after.

What the wrong stamp count costs you in December

Postage mistakes are small per envelope and real per batch. A book of 20 Forever stamps now costs $16.40, and 50 standard holiday cards cost $41.00 to mail at the 1 ounce rate. If 10 of those 50 are square, the surcharge adds $4.90.

Overpaying with Forever stamps only

Using only Forever stamps on a 2 ounce letter wastes 53 cents every time, $1.64 paid against $1.11 owed. Mail 20 heavy wedding invitations that way and you've given away $10.60. A sheet of additional-ounce stamps fixes it.

Postcards are the cheap option

A postcard mails for $0.65, which is 17 cents less than a letter, as long as it's 5 to 6 inches long and 3.5 to 4.25 inches high. Swap 50 holiday letters for postcards and you keep $8.50, with no envelope to weigh at all.

A $16.40 book of 20 Forever stamps covers 20 one-ounce letters, but only 6 large envelopes weighing 3 ounces each.

Questions people ask before dropping it in the mailbox

How much is a stamp right now?

A Forever stamp costs 82 cents as of July 12, 2026, and a postcard stamp costs 65 cents. Forever stamps you bought at 78 cents still work on a 1 ounce letter, because they're valid at whatever the current First-Class rate is.

How much does a stamp cost for a letter going abroad?

An international letter up to 1 ounce costs $1.75, the same price a Global Forever stamp sells for. You can also make up the amount with three domestic Forever stamps, but that's $2.46 and overpays by 71 cents.

Is a USPS postage price calculator worth it for letters?

For a standard 1 ounce letter, no, the stamp math above is the whole story. A USPS price calculator earns its keep with flats over 3 ounces, packages and international mail, where the tiers multiply. Any postage calculator still asks for the weight, so you need a number first.

How do I weigh a letter without a postal scale?

A kitchen scale that reads in grams works fine, as long as it's accurate at light weights. Our scale calibration guide walks through a quick coin check. Anything under 28 grams is a one-stamp letter.

Need to weigh a card or letter fast? Download Scale for Grams and get an AI-powered weight estimate from a photo in seconds, so you know whether that envelope needs one stamp or two before you hit the post office. Get the app here: iOS.