Large envelope postage costs $1.69 for 1 ounce in 2026
A large envelope, which USPS calls a flat, is bigger than a letter, like a 9 by 12 inch envelope. It costs $1.69 to mail at 1 ounce. Each extra ounce adds about $0.29 to $0.31, up to $5.24 at 13 ounces.
Large envelope (flat) prices from USPS
| 1 ounce | $1.69 |
|---|---|
| 2 ounces | $1.98 |
| 3 ounces | $2.27 |
| 4 ounces | $2.56 |
| 5 ounces | $2.85 |
| 6 ounces | $3.14 |
| 7 ounces | $3.43 |
| 8 ounces | $3.72 |
| 9 ounces | $4.02 |
| 10 ounces | $4.32 |
| 11 ounces | $4.62 |
| 12 ounces | $4.93 |
| 13 ounces | $5.24 |
A flat is 11.5 to 15 inches long, 6.125 to 12 inches high and 0.25 to 0.75 inch thick. Rigid, uneven or odd shaped envelopes pay package prices. Source: USPS Notice 123, Price List, effective July 12, 2026 (Postal Explorer).
What changes your price
- Weight. Each ounce adds about $0.29 to $0.31.
- Shape. If it is stiff or lumpy, it pays package prices, not flat prices.
Ways to pay less
- Keep it flat and flexible so it stays a flat.
- Fold papers into a letter envelope if you can. A 1 ounce letter is $0.82.
How we got these numbers
USPS sets one national price for large envelope postage. Every price on this page comes from USPS Notice 123, the official price list the Postal Service publishes. The prices we use took effect on July 12, 2026. Where we show a total, we simply add up the separate USPS fees, so you can see what one item costs all in. We do not add our own guesses or use a calculator, because USPS sets these fees and they are the same at every Post Office. USPS changes its prices from time to time, so check the price at the counter if your visit is far from September 26, 2026, the day we last checked.
Common questions
How much to mail a 9 by 12 envelope?
$1.69 at 1 ounce, plus about $0.29 per extra ounce.
How many stamps for a large envelope?
At 1 ounce, $1.69 in postage, which is more than two $0.82 Forever stamps.
What is the heaviest flat?
13 ounces, at $5.24.