Direct answer: A qualifying domestic large envelope (flat) costs $1.69 for 1 ounce as of July 12, 2026. Because an ordinary Forever stamp is worth $0.82, two total $1.64 and are not enough; three pay $2.46. The correct count changes with weight, and a rigid, lumpy, nonrectangular, or oversized envelope may be charged as a parcel instead.
2026 Large Envelope Postage and Forever Stamp Count
| Weight | Flat postage | Minimum 82-cent Forever stamps | Postage applied |
|---|---|---|---|
| 1 oz. | $1.69 | 3 | $2.46 |
| 2 oz. | $1.98 | 3 | $2.46 |
| 3 oz. | $2.27 | 3 | $2.46 |
| 4 oz. | $2.56 | 4 | $3.28 |
| 5 oz. | $2.85 | 4 | $3.28 |
| 6 oz. | $3.14 | 4 | $3.28 |
| 7 oz. | $3.43 | 5 | $4.10 |
| 8 oz. | $3.72 | 5 | $4.10 |
| 9 oz. | $4.02 | 5 | $4.10 |
| 10 oz. | $4.32 | 6 | $4.92 |
| 11 oz. | $4.62 | 6 | $4.92 |
| 12 oz. | $4.93 | 7 | $5.74 |
| 13 oz. | $5.24 | 7 | $5.74 |
The stamp counts round up because USPS does not refund overpaid postage. To reduce overpayment, combine one or more Forever stamps with smaller-denomination stamps that reach at least the required total.
First Confirm That the Envelope Qualifies as a Flat
A First-Class Mail large envelope must be rectangular, flexible, uniformly thick, no more than 15 inches long, 12 inches high, and 3/4 inch thick, and no more than 13 ounces. It becomes a flat because it exceeds at least one letter maximum: 11-1/2 inches long, 6-1/8 inches high, or 1/4 inch thick.
USPS says a large-envelope-sized piece that is rigid, nonrectangular, or not uniformly thick pays parcel prices. Clasps, bulky contents, uneven objects, and stiff backing can therefore change the answer even when the outside dimensions appear to fit.
What About Common Envelope Sizes?
- 10 x 13: within the flat maximums, but only if the finished piece is flexible, uniformly thick, rectangular, 3/4 inch or less thick, and 13 ounces or less.
- 8.5 x 11: its height exceeds the letter maximum, so it can use flat pricing when the other flat conditions are met.
- 8 x 10: also exceeds the letter-height limit and can qualify as a flat under the remaining rules.
- “Oversized envelope”: the name alone is not enough. Measure the sealed, filled mailpiece and test its flexibility and uniform thickness.
Calculation Method
- Enter the destination and confirm this is domestic mail.
- Measure the finished length, height, and thickness.
- Check rectangular shape, flexibility, and uniform thickness.
- Weigh the sealed envelope and round up to the next whole-ounce price step.
- Find the current flat price in USPS Notice 123.
- Divide that price by the current Forever value and round the stamp count up, or combine denominations more precisely.
For the final classification, use the USPS postage calculator or take the finished piece to a Post Office. You can also use the site’s postage decision guide.
Frequently Asked Questions
Can Forever stamps be used on a large envelope?
Yes. Each valid ordinary Forever stamp contributes its current value. The total postage must still meet the price for the finished mailpiece.
Are two Forever stamps enough for a large envelope?
No for the current 1-ounce domestic flat price: two are worth $1.64, which is 5 cents short of $1.69. Use three ordinary Forever stamps or a more exact combination of valid denominations.
How many Forever stamps for a 6-ounce large envelope?
The current flat price is $3.14. Four ordinary Forever stamps provide $3.28, assuming the piece actually qualifies as a flat.
How many Forever stamps for an 11-ounce large envelope?
The current flat price is $4.62. Six ordinary Forever stamps provide $4.92, subject to flat eligibility.
What happens above 13 ounces?
It no longer qualifies for First-Class Mail flat pricing. Use the USPS calculator to select an eligible parcel or other service based on the finished piece and destination.
Sources checked August 31, 2026: USPS Notice 123 price list; USPS physical standards; USPS letters and postcards guidance. Rates and classifications can change.