Postcard size guide
Postcard sizes and dimensions
The standard US postcard is 4 × 6 inches. Below: every common postcard size in inches, millimeters, and pixels, which USPS price each one mails at, and how to address a postcard so it gets delivered.
Common postcard sizes at a glance
Pixel sizes are at 300 DPI, the standard for print. "With bleed" adds the ⅛ inch on each side that printers trim off.
| Size | Inches | Millimeters | Pixels (300 DPI) | With bleed | USPS mails it as |
|---|---|---|---|---|---|
| 4 × 6 | 4 × 6 in | 101.6 × 152.4 mm | 1200 × 1800 | 1275 × 1875 | Postcard The standard postcard. Smallest, cheapest to mail one at a time. |
| A6 | 4.13 × 5.83 in | 105 × 148 mm | 1240 × 1748 | 1315 × 1823 | Postcard The international standard. Fits under the USPS postcard maximum. |
| 5 × 7 | 5 × 7 in | 127 × 177.8 mm | 1500 × 2100 | 1575 × 2175 | Letter Too big for the postcard price — mails at the letter price. |
| 6 × 9 | 6 × 9 in | 152.4 × 228.6 mm | 1800 × 2700 | 1875 × 2775 | Letter Popular marketing size; still letter-sized (6 in is under 6⅛ in). |
| 6 × 11 | 6 × 11 in | 152.4 × 279.4 mm | 1800 × 3300 | 1875 × 3375 | Letter The largest common letter-sized card. |
| 6.5 × 9 | 6.5 × 9 in | 165.1 × 228.6 mm | 1950 × 2700 | 2025 × 2775 | Flat (EDDM) Taller than 6⅛ in, so it qualifies for Every Door Direct Mail. Ours. |
| 8.5 × 11 | 8.5 × 11 in | 215.9 × 279.4 mm | 2550 × 3300 | 2625 × 3375 | Flat (EDDM) Jumbo card or flyer size; EDDM-eligible. |
The USPS size rules: postcard, letter, or flat
USPS doesn't price a card by what you call it — it prices it by size. Every card falls into one of three classes:
Postcard
3.5 × 5 in up to 4.25 × 6 in, 0.007–0.016 in thick.
The cheapest single-piece price. Only small cards qualify.
Letter
Up to 6⅛ × 11½ in, up to ¼ in thick.
Most marketing cards (5 × 7, 6 × 9, 6 × 11) mail here.
Flat
Taller than 6⅛ in or longer than 11½ in, up to 12 × 15 in.
Required for Every Door Direct Mail (EDDM).
Two more rules catch people out: the card's length divided by its height should be between 1.3 and 2.5 (a square card costs more to mail), and it needs to be at least 0.007 inches thick — roughly the stiffness of an index card.
Which postcard size should a business use?
Mailing to a list one by one. 4 × 6 is the cheapest to mail, but the smallest thing in the mailbox. 6 × 9 is the common upgrade for marketing.
Mailing whole neighborhoods (EDDM). You need a flat: 6.5 × 9, 6.25 × 11, or 8.5 × 11. No list, no addresses, and the lowest postage per piece.
Standing out. Bigger wins attention. A card larger than everything else in the stack is the one that gets picked up first.
Designing one? Our postcard design guide covers layout, bleed, and safe zones.
How to address a postcard
Turn the card to the side without the picture. Draw an imaginary line down the middle: the left half is for your message, the right half is for the address.
- Stamp: top-right corner.
- Recipient address: on the right half, about halfway down — name, street address, then city, state, and ZIP code on the last line.
- Return address (optional): top-left corner of the address side, so an undeliverable card can come back.
- Keep the bottom clear: leave the bottom ⅝ inch blank along the right side. USPS prints a sorting barcode there.
- International: add the country on the last line in capital letters, in English.
Mailing a whole neighborhood? You don't address anything.
With Every Door Direct Mail, the card goes to every mailbox on the postal routes you pick. There are no names or addresses — the card carries a printed postage mark and the line "ECRWSS Local Postal Customer" instead. It's the easiest way to reach a few thousand nearby households without buying a mailing list.
Postcard size FAQs
What is the standard postcard size?
In the US the standard postcard is 4 × 6 inches (101.6 × 152.4 mm). To mail at the USPS postcard price, a card must be between 3.5 × 5 inches and 4.25 × 6 inches, and between 0.007 and 0.016 inches thick. Anything larger mails at the letter or flat price.
Are most postcards 4x6 or 5x7?
Most personal and souvenir postcards are 4 × 6. Marketing postcards are usually bigger — 5 × 7, 6 × 9, 6 × 11, or larger — because a bigger card stands out in the mailbox. The trade-off is that anything over 4.25 × 6 inches no longer qualifies for the postcard price.
Can I mail a 5x7 card as a postcard?
You can mail it, but not at the postcard price. A 5 × 7 card is larger than the 4.25 × 6 inch postcard maximum, so USPS charges it the letter price. It still needs no envelope, as long as it's stiff enough (at least 0.007 inches thick).
Are postcards usually A5 or A6?
A6 (105 × 148 mm, about 4.1 × 5.8 inches) is the international standard postcard size and the closest match to the US 4 × 6. A5 (148 × 210 mm) is twice as big and is used more for flyers. An A6 card fits under the USPS postcard maximum, so it mails at the postcard price in the US.
What are USPS rules for postcards?
To qualify for the postcard price a card must be rectangular, 3.5–4.25 inches tall, 5–6 inches long, and 0.007–0.016 inches thick. Its length divided by its height should fall between 1.3 and 2.5, or it may be charged a non-machinable surcharge. The address side needs a clear area for the address and the barcode along the bottom.
What size postcard do I need for Every Door Direct Mail (EDDM)?
EDDM Retail only accepts flats: the piece must be taller than 6⅛ inches, longer than 11½ inches, or thicker than ¼ inch, and no bigger than 12 × 15 inches. A 4 × 6 or 6 × 9 card is too small. Common EDDM sizes are 6.5 × 9, 6.25 × 11, and 8.5 × 11. Our cards are 6.5 × 9.
What resolution should a postcard file be?
Print files should be 300 DPI at the final size, plus ⅛ inch of bleed on every side. A 4 × 6 postcard is 1200 × 1800 pixels at the trim, or 1275 × 1875 pixels with bleed. The table above lists the pixel sizes for every common size.
Do you put a return address on a postcard?
It's optional but recommended. Put it in the top-left corner of the address side. Without one, an undeliverable postcard can't come back to you. EDDM postcards don't need a return address or a recipient address at all.
How do I address an international postcard?
Write the address the same way, and put the destination country on the last line in capital letters and in English (for example, CANADA). Use international postage — a domestic stamp isn't enough.
Skip the sizing and addressing entirely
We design, print, and deliver 6.5 × 9 postcards to the neighborhoods that fit your business — no mailing list, no addresses, no stamps.