Postcard Stamps vs Forever Stamps: Which One Do You Need?
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Sending a postcard? Use a postcard stamp and pay less. Mailing a standard letter or hedging against future rate hikes? A Forever stamp is the safer buy. That's the whole postcard stamps vs Forever stamps decision in two sentences — but the reason the choice trips people up is that both stamps are "forever" in their own way, and one can substitute for the other while the reverse doesn't work.
Here's what most guides skip: the postcard stamp you buy at the post office today is itself a Postcard Forever stamp. It locks in the current postcard rate even if prices climb. So you're not really choosing between "forever" and "not forever." You're choosing which mailpiece you're covering.
Postcard Stamp vs Forever Stamp
| Postcard Stamp | First-Class Forever Stamp | |
|---|---|---|
| Covers | 1 domestic postcard within size limits | 1-ounce domestic letter |
| Rate-lock (Forever) | Yes — holds the postcard rate | Yes — holds the 1-oz letter rate |
| Use it on a letter? | No — underpays postage | Yes |
| Use it on a postcard? | Yes | Yes, but you overpay |
| Best for | Postcards, direct mail, bulk cards | Letters, mixed mail, stockpiling |
A First-Class Forever stamp covers a standard 1-ounce letter and never expires (USPS, usps.com/ship/letters.htm). A postcard stamp covers one qualifying postcard at a lower price. The gap between them runs roughly ten cents per piece — small on a birthday card, real money on a mailing list.
One caveat before you buy: USPS adjusts postage periodically, so check the live number at usps.com before you stock up. Any price printed in a blog (including the figures below) can go stale between rate changes.
Can a Forever Stamp Go on a Postcard?
Yes. A First-Class Forever stamp fully covers a postcard — the post office won't reject it. You'll just pay the letter rate when the card only needed the postcard rate, so you're throwing away the difference (about a dime) on every card.
For one vacation postcard, who cares. For a save-the-date going to 300 households, that dime turns into $30 you didn't need to spend. That's the entire argument for keeping postcard stamps on hand instead of reaching for whatever's in the drawer.
Can a Postcard Stamp Go on a Letter?
No. A single postcard stamp doesn't carry enough value for a 1-ounce letter, and USPS treats it as short-paid. The mail either comes back to you or lands on your recipient's doorstep with postage due — an awkward look for a wedding invite.
You can combine stamps to reach the letter rate. Stick a postcard stamp plus additional postage on the envelope and, as long as the total meets or beats the current 1-ounce price, it mails fine. Most people find it simpler to keep both denominations around than to do stamp arithmetic at the kitchen table.
USPS Postcard Size Rules
A card only earns the cheaper postcard rate if it fits inside USPS dimensions. Go bigger, thicker, or square, and USPS bumps it to letter postage — meaning your postcard stamp no longer covers it.
| Requirement | Qualifies for Postcard Rate |
|---|---|
| Minimum size | 3.5 in high × 5 in long |
| Maximum size | 4.25 in high × 6 in long |
| Maximum thickness | 0.016 in |
| Shape | Rectangular (square cards don't qualify) |
Verify these thresholds at usps.com/ship/postcards before a large order — printers sometimes cut "postcards" that are technically letter-size. A 5×7 card is a letter as far as USPS is concerned, even though everyone calls it a postcard.
What happens if you underpay an oversized card with a single postcard stamp? Same as the letter scenario: it's returned to sender or delivered postage-due. For Postcrossing members and hobbyist mailers sending art cards, this is the quiet trap — the card looks like a postcard but mails like a letter.
Bulk Sender Math
This is where the choice stops being trivia. At a roughly ten-cent per-piece gap, using postcard stamps instead of Forever stamps on qualifying cards adds up fast.
| Postcards Mailed | Approx. Savings vs. Forever Stamps |
|---|---|
| 50 | ~$5 |
| 100 | ~$10 |
| 500 | ~$50 |
| 1,000 | ~$100 |
Run a real-estate farm route, a small-shop promo, or a nonprofit appeal, and that's a printing budget you just handed back to yourself. The math assumes every card meets the size rules above — one oversized design and the whole run jumps to letter rate. For teams buying at volume, sourcing wholesale postcard stamps is usually cheaper per piece than grabbing Forever books retail. If you're stockpiling letter postage too, weigh discount Forever stamps against face value.
International Postcards
Neither a domestic postcard stamp nor a standard Forever stamp pays enough for an international postcard. Mail leaving the US needs the Global Forever stamp (or the equivalent international rate in combined postage), which costs several times the domestic postcard rate.
Postcrossing members trip on this constantly: a card that's cheap to mail within the US costs far more once it crosses a border. Check the current Global Forever price at usps.com and buy those separately — don't assume your domestic stamps stretch abroad.
Which Stamp Should You Buy?
Walk it in this order:
- Is it going abroad? Buy a Global Forever stamp. Stop here.
- Is it a postcard within 4.25 × 6 inches and rectangular? A postcard stamp is the cheapest correct choice.
- Is it a letter, an oversized card, or a square card? Use a First-Class Forever stamp.
- Do you mail a mix and hate sorting? Keep Forever stamps for letters and a book of postcard stamps for cards — the ten-cent savings pays for the minor hassle within one bulk run.
If you can't measure the card or you're buying ahead of a rate change with no specific card in mind, Forever stamps are the safer hedge — they cover more situations. Postcard stamps win when you know the card qualifies and you're sending enough to make the per-piece savings matter.
FAQ
Are postcard stamps forever stamps too?
Yes. Modern USPS postcard stamps are Postcard Forever stamps — they stay valid at the current postcard rate even after a price increase, so no top-up sticker is needed later.
How many forever stamps does a postcard need?
One First-Class Forever stamp fully covers a standard postcard. You'll overpay by roughly a dime versus a postcard stamp, since the Forever stamp is priced for a 1-ounce letter.
How much would 100 postcard stamps cost?
Multiply 100 by the current postcard rate at usps.com. Against Forever stamps, buying postcard stamps for those 100 cards saves you about $10 at the typical ten-cent per-piece gap.
Can I use regular postage stamps for postcards?
Yes, a regular Forever stamp works on a postcard and covers full postage — you just pay the letter rate. It won't be rejected; you're only overpaying the difference.
Deciding between denominations is easier when the stamps are authentic and priced below face. At Mailboxes of Flushing, we source unused stamps from closed businesses, inspect every one for flawless, unbent condition, and ship within 24 hours — so whether you need a book of postcard stamps for a mailing run or Forever stamps to keep on hand, browse our postcard and Forever stamp collections and buy exactly what your next card calls for.