Yes, you can put two stamps on an envelope. The U.S. Postal Service adds up the face value of every stamp you affix, so two stamps deliver your mail as long as their combined value meets or exceeds the required postage. Two Forever stamps come to $1.56, which more than covers a standard one-ounce First-Class letter at $0.78 and handles almost any domestic letter you’re likely to send.1United States Postal Service. Notice 123 Price List
How USPS Counts Multiple Stamps
Every stamp on the envelope contributes its face value toward the postage total. Mix and match freely. A Forever stamp counts for the current one-ounce First-Class rate of $0.78 on the day you mail, no matter what you paid for it originally.2United States Postal Service. Fact Sheet: Forever Stamp Older stamps printed with a specific dollar amount (a 37¢ or 55¢ stamp from a drawer) stay valid too, and you can combine them with anything else to reach the amount you need.
USPS also sells small-denomination stamps in 1¢, 2¢, 3¢, 4¢, 5¢, and 10¢ values specifically so you can build the exact amount.3USPS. How to Send a Letter or Postcard If your envelope needs $1.07, one Forever stamp plus one additional-ounce stamp ($0.29) gets you there precisely.
Put every stamp on the address side, in the upper-right corner.3USPS. How to Send a Letter or Postcard Line them up neatly. Stamps on the back of the envelope or scattered across the front can cause problems with automated sorting.
What Two Forever Stamps Actually Cover
At $1.56 combined, two Forever stamps cover any domestic First-Class letter up to 3.5 ounces, which is the maximum weight for letter-rate mail.4USPS. First-Class Mail and Postage A 3.5-ounce letter costs $1.65, so you’d actually need a bit more than two Forever stamps at the very top of the range, but anything through roughly three ounces ($1.36) is comfortably covered.1United States Postal Service. Notice 123 Price List
Two stamps also solve the square-envelope problem. Square greeting cards, rigid envelopes, and other unusually shaped mailpieces carry a $0.49 nonmachinable surcharge because they jam automated sorting equipment.1United States Postal Service. Notice 123 Price List A one-ounce square birthday card costs $1.27 rather than $0.78, and two Forever stamps clear that easily.5Postal Explorer. Sizes for Letters
When Two Stamps Aren’t Enough
Large Envelopes
Letter rates only apply if the envelope stays within 6⅛ inches tall, 11½ inches long, and ¼ inch thick.5Postal Explorer. Sizes for Letters Anything larger jumps to “large envelope” (flat) pricing, which starts at $1.63 for the first ounce. Two Forever stamps ($1.56) fall a few cents short. You’d need a third stamp, or add a small-denomination stamp to make up the difference.
International Mail
A one-ounce letter to any country, including Canada and Mexico, costs $1.70.6USPS. 2026 Postage Price Change Two domestic Forever stamps ($1.56) don’t cover it. Domestic Forever stamps are valid on international mail, but you’ll need three of them ($2.34) or additional postage to clear the $1.70 threshold.7USPS Postal Bulletin. Frequently Asked Questions A single Global Forever stamp covers a one-ounce international letter at exactly $1.70.
What Happens If the Postage Is Wrong
If your envelope is shortpaid and has a return address, USPS sends it back with a “Returned for Additional Postage” notice showing how much more is owed. Sometimes shortpaid mail is forwarded to the recipient, who is asked to pay the difference before delivery. Without a return address, if the recipient refuses to pay, the envelope ends up as dead mail at a postal recovery center.8United States Postal Service. P011 Payment Include a return address so a shortpaid piece comes back to you rather than disappearing.
Overpaying is not a delivery problem, but USPS does not refund the extra. Two Forever stamps on a plain one-ounce letter means you’ve spent $0.78 more than necessary. Fine on a single envelope; expensive across a stack of wedding invitations. Small-denomination stamps let you hit the required amount exactly when it matters.
Common Stamp Combinations
- Standard letter (1 oz): one Forever stamp ($0.78)
- Two-ounce letter: one Forever stamp plus one additional-ounce stamp ($1.07)
- Square greeting card (1 oz): one Forever stamp plus $0.49 in additional stamps ($1.27), or two Forever stamps
- Large envelope (1 oz): three Forever stamps ($2.34), or exact postage of $1.63
- International letter (1 oz): one Global Forever stamp ($1.70), or three domestic Forever stamps ($2.34)
- Postcard: one postcard stamp ($0.61)
If you’re unsure what your envelope weighs or whether it counts as a letter or a flat, hand it to a clerk at the post office counter. Weighing and rate lookup are free, and you’ll leave knowing exactly which stamps to use.