Direct answer: “Manila envelope” describes the envelope, not its USPS mail class. A flexible, uniformly thick 6 x 9 envelope can qualify as a letter and may need one 82-cent Forever stamp at 1 ounce. A flexible 9 x 12 or 10 x 13 envelope normally falls under large-envelope (flat) dimensions; the current 1-ounce flat price is $1.69, so two Forever stamps are short and three are needed if using only ordinary Forever stamps.
Common Manila Envelope Examples
| Finished envelope | Likely class if flexible and uniform | Current postage | Forever stamps alone |
|---|---|---|---|
| 6 x 9, up to 1 oz. | Letter | $0.82 | 1 |
| 6 x 9, over 1 up to 2 oz. | Letter | $1.11 | 2 = $1.64 |
| 6 x 9, over 2 up to 3 oz. | Letter | $1.40 | 2 = $1.64 |
| 9 x 12 or 10 x 13, up to 1 oz. | Large envelope (flat) | $1.69 | 3 = $2.46 |
| 9 x 12 or 10 x 13, over 1 up to 2 oz. | Large envelope (flat) | $1.98 | 3 = $2.46 |
| 9 x 12 or 10 x 13, over 2 up to 3 oz. | Large envelope (flat) | $2.27 | 3 = $2.46 |
| 9 x 12 or 10 x 13, over 3 up to 4 oz. | Large envelope (flat) | $2.56 | 4 = $3.28 |
Rates are effective July 12, 2026. The stamp counts round up and may overpay. Smaller denominations can make the total more exact.
Letter, Flat, or Parcel?
- Letter: no more than 11-1/2 inches long, 6-1/8 inches high, 1/4 inch thick, and 3.5 ounces.
- Large envelope (flat): exceeds at least one letter maximum but is no more than 15 inches long, 12 inches high, 3/4 inch thick, and 13 ounces.
- Parcel-priced piece: a flat-sized item that is rigid, nonrectangular, or not uniformly thick.
A clasp, cardboard stiffener, key, pen, thick stack, uneven object, or other rigid content can change the classification. Measure and test the sealed envelope, not the empty package.
Five-Step Calculation
- Seal the final contents and weigh the entire envelope.
- Measure length, height, and maximum thickness.
- Check that it is rectangular, flexible, and uniformly thick.
- Select letter, flat, or package pricing before calculating stamps.
- Use the USPS postage calculator or a Post Office counter for the final amount.
For the full 1-13 ounce flat table, see How Many Forever Stamps for a Large Envelope?.
Frequently Asked Questions
Can I use Forever stamps on a manila envelope?
Yes. Each valid ordinary Forever stamp contributes 82 cents at the current rate. The combined value must cover the correctly classified mailpiece.
Are two Forever stamps enough for a 9 x 12 manila envelope?
No for a qualifying 1-ounce domestic flat: two equal $1.64, which is 5 cents short of the current $1.69 price.
Does a 6 x 9 manila envelope need two stamps?
Not automatically. If it qualifies as a machinable letter and weighs no more than 1 ounce, one ordinary Forever stamp currently covers it. More weight or a nonmachinable characteristic changes the amount.
What if the envelope contains documents and cardboard?
Cardboard can make the item rigid. A rigid flat-sized envelope may pay package prices, so check the finished piece at a Post Office rather than relying on a flat stamp count.
Is “manilla envelope” a different product?
No. “Manilla” is a common misspelling of manila. USPS classification still depends on the finished mailpiece, not the spelling or material name.
Sources checked August 31, 2026: USPS Notice 123; USPS physical standards; USPS letters guidance.