A Guide to Pairing Postcards and Envelope Sizes
A 4 by 6 postcard slides into an A6 envelope, a 5 by 7 into an A7, a 5.5 by 8.5 into an A9. Here is how every standard postcard size lines up with the envelope that fits it, plus when to skip the envelope and mail bare.
To pair a postcard with an envelope, pick the envelope about a quarter inch larger on each side. A 4x6 postcard fits an A6 (4.75 x 6.5), a 5x7 fits an A7 (5.25 x 7.25), and a 5.5 x 8.5 fits an A9 (5.75 x 8.75). Any postcard up to 4.25 x 6 also mails bare at the USPS postcard rate with no envelope at all.
Quick answer
The short version of postcard and envelope sizes
Match the envelope to the postcard, not the other way around. Standard postcards come in 4 by 6, 5 by 7, 5.5 by 8.5, and 6 by 9 inches. The A-series envelopes are cut to hold them, so a 4x6 slides into an A6, a 5x7 into an A7, and a 5.5 x 8.5 into an A9. Give the envelope about a quarter inch of clearance on each side. If you are running a promo and want the lowest postage, keep the card at or below 4.25 by 6 inches and mail it bare at the postcard rate. Print the card and the envelope together at 4OVER4.COM and the paper, ink, and finish stay consistent across the whole mailer.
Standard postcard sizes
Almost every postcard you have ever pulled from a mailbox is one of a handful of sizes. Printers and the postal service settled on these dimensions decades ago, and sticking to them is what keeps your card cheap to mail and easy to slip into an envelope later.
- 4" x 6" is the workhorse. It qualifies for the USPS postcard rate, costs the least to send, and is the size most direct mail runs on. Our Direct Mail Postcards are built around it.
- 4.25" x 5.5" is the compact quarter-page size, common for reply cards and thank-you notes.
- 5" x 7" reads as an invitation. It is bigger, feels more personal, and moves up to the letter rate.
- 5.5" x 8.5" is the half-page format for promos that need to shout.
- 6" x 9" and 6" x 11" are the jumbo sizes that dominate a stack of mail while still shipping at the letter rate. See our Oversized Postcards for these.
If you are not sure which size suits the message, our Online Designer lets you drop your artwork onto each format and see how the layout breathes before you commit. You can browse the full range on the postcard printing page.
Standard envelope sizes that fit each postcard
When you do want an envelope, reach for the announcement series, usually written as A2, A6, A7, and A9. These are the cream-colored invitation envelopes, and they exist specifically to hold card-shaped inserts. Each one is cut a little larger than a common postcard so the card slides in without a struggle.
- A2 (4.375" x 5.75") holds a 4.25 by 5.5 reply card.
- A6 (4.75" x 6.5") is the natural home for a 4 by 6 postcard.
- A7 (5.25" x 7.25") takes a 5 by 7 invitation card.
- A9 (5.75" x 8.75") carries a 5.5 by 8.5 half-page piece.
- 6.5" x 9.5" catalog envelopes swallow a 6 by 9 jumbo card.
You can order these ready to print or blank to run through your own inkjet. Our Printed Envelopes arrive with your return address and branding already on them, while Blank Envelopes keep it simple. Browse the whole lineup under envelope printing, and if a term throws you, the printing terms glossary spells it out.
How to match postcards with the right envelope
The matching math is refreshingly simple. Your envelope wants to be about a quarter inch larger than the card on both the width and the height. That gap is enough for the card to go in and come out without creasing, and small enough that it does not slide around inside.
Work in this order. First, lock the postcard size to the message and the postage you want. Second, find the A-series envelope that clears the card by roughly a quarter inch on each side. Third, decide whether the card even needs the envelope, because a bare 4 by 6 at the postcard rate is the cheapest mailer there is.
A couple of things to watch. Heavier card stock and any liner eat into that clearance, so lean toward the roomier envelope if you are printing on thick paper. And if you are addressing through a window, make sure the card sits high enough that the address does not disappear below the cutout. When you print the card and the envelope together, we keep the stock and coating consistent so the whole set feels intentional. Need to send in volume? The direct mail postcard walkthrough covers the mailing side.
Order the pair
Postcards and envelopes, printed to match
Three formats that cover most mailers, printed in-house so the card and its envelope share the same stock and color.
Size chart
Postcard-to-envelope size chart
Each standard postcard on the left, and the envelope built to hold it on the right. Every envelope leaves roughly a quarter inch of clearance on each side.
Recommended pairings
Recommended postcard and envelope pairings
A quick reference for the pairing that fits each job, with the 4OVER4.COM product that prints it.
| Postcard size | Matching envelope | Best for | Print it at 4OVER4 |
|---|---|---|---|
| 4" x 6" | A6 (4.75" x 6.5") | Everyday mailers, save-the-dates, coupons | Direct Mail Postcards |
| 4.25" x 5.5" | A2 (4.375" x 5.75") | Reply cards, thank-you notes, RSVPs | Standard Postcards |
| 5" x 7" | A7 (5.25" x 7.25") | Invitations, greeting-style postcards | Standard Postcards |
| 5.5" x 8.5" | A9 (5.75" x 8.75") | Announcements, high-impact promos | Oversized Postcards |
| 6" x 9" | 6.5" x 9.5" Catalog | Newsletters, menus, jumbo mailers | Oversized Postcards |
Postcards larger than 6 by 9 inches, like a 6 by 11, usually mail bare at the First-Class letter rate rather than inside an envelope. When in doubt, weigh a finished sample at the post office before you commit to a full run.
Specs and pricing
Postcard and envelope specs, side by side
The live options for a standard postcard and a blank envelope, straight from the configurator, plus per-unit pricing on our most-ordered direct mail postcard.
| Quantity | Price Per Unit | Total |
|---|---|---|
| 500 | 17.9¢ | $89.68 |
| 1,000 | 17.1¢ | $170.53 |
| 2,000 | 9.35¢ | $186.95 |
| 3,000 | 6.84¢ | $205.13 |
| 4,000 | 5.58¢ | $223.31 |
| 5,000 | 4.83¢ | $241.51 |
| 6,000 | 4.56¢ | $273.85 |
| 7,000 | 4.37¢ | $306.18 |
Wally sizes up the pair
The right envelope is a quarter inch bigger, no more
Wally thinks of an envelope like a parking space: leave a little room on every side and the card glides in, cut it too tight and it creases at the door. Start from the postcard size, step up to the A-series envelope that clears it by about a quarter inch, and you are done. Print the card and the envelope in one run at 4OVER4 so the color and paper match, and if the piece fits the postcard rate, skip the envelope entirely and save on postage.
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Common Questions
Common questions about postcard and envelope sizes
What size envelope fits a 4x6 postcard?
An A6 envelope, which measures 4.75 by 6.5 inches, is the standard match for a 4 by 6 postcard. It leaves about a quarter inch of clearance on each side so the card slides in cleanly without bending. If you want a snugger fit for a premium feel, a 4.5 by 6.25 inch envelope also works.
Do I actually need an envelope to mail a postcard?
No. That is the whole point of a postcard. Anything up to 4.25 by 6 inches and between 0.007 and 0.016 inches thick qualifies for the USPS postcard rate and mails bare, with no envelope required. People add envelopes when they want privacy, a formal presentation for an invitation, or room to enclose a reply card.
What is the largest postcard I can mail without an envelope?
To keep the discounted USPS postcard rate, stay within 4.25 by 6 inches. Go bigger and the piece is still mailable, but it moves up to the First-Class letter rate. Once you pass 6.125 by 11.5 inches it becomes a flat, which costs more again. Oversized postcards up to 6 by 11 are popular precisely because they still mail as a letter.
Should the envelope be bigger than the card?
Yes, always. A good rule is roughly a quarter inch larger than the card on both the width and the height. Too tight and the card creases going in, too loose and it slides around and looks sloppy through the address window. The A-series envelope sizes are already spaced for common card dimensions, which takes the guesswork out.
What envelope holds a 5x7 postcard?
An A7 envelope, at 5.25 by 7.25 inches, is the go-to for a 5 by 7 card. It is the size most people reach for with invitations and greeting-style postcards. If you plan to add a liner or a heavier card stock, the A7 still has enough room to close flat.
Can I print the postcards and envelopes together?
Yes, and it is the smoother path. Ordering both in one run at 4OVER4.COM keeps the ink color, paper weight, and coating consistent across the set, so the envelope and the card read as one designed piece rather than two mismatched parts. It also means a single turnaround instead of chasing two suppliers.
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Pick your size, drop in your artwork, and we print a matched postcard and envelope set that mails clean and looks like one designed piece.
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