Mango Postal
What Is the Standard Postcard Size? (Canada and US Dimensions)
The standard postcard size is 4 × 6 inches (101 × 152 mm). It's the size most people picture when they think "postcard," it fits every postal system's rules, and it's the size we print at Mango Postal.
If you're designing or printing your own, here's what the post office actually allows, and which sizes cost more to mail.
Common postcard sizes
| Size (inches) | Size (mm) | Good for | Mails at postcard rate in the US? |
|---|---|---|---|
| 4 × 6 | 101 × 152 | Photos, travel cards, everyday postcards | Yes |
| 4.25 × 6 | 108 × 152 | The largest US postcard-rate size | Yes |
| 5 × 7 | 127 × 178 | Invitations, art prints | No (letter rate) |
| 6 × 9 | 152 × 229 | Business mailers, big visuals | No (letter rate) |
4 × 6 is the sweet spot. It's the same ratio as a phone photo (3:2), so your pictures fit without awkward cropping. For how the postcard itself began, see our short history of postcards.
Postcard size rules in Canada
Canada Post treats postcards as standard-size mail. To mail one:
- Smallest: 140 × 90 mm (5.51 × 3.54 in)
- Largest: 245 × 156 mm (9.65 × 6.14 in) within Canada, or 235 × 120 mm (9.25 × 4.72 in) to the US and other countries
- Minimum thickness: 0.18 mm (0.007 in)
- Maximum weight: 50 g for standard-size mail
A 4 × 6 card (152 × 101 mm) sits comfortably inside those limits. Anything thinner than 0.18 mm is too flimsy for the sorting machines, so regular printer paper won't work.
Postcard size rules in the US
USPS is stricter. To get the cheaper postcard stamp ($0.65 in 2026), the card must be:
- At least 3.5 × 5 in
- At most 4.25 × 6 in
- Between 0.007 and 0.016 in thick
Go any bigger (a 5 × 7, say) and it's charged as a letter ($0.82 with a Forever stamp). More on prices in how much is a postcard stamp.
What paper thickness should a postcard be?
The legal minimum is about 0.18 mm, but a card that thin feels cheap and bends in the mail. We print on 1 mm (40 mil), 500 gsm, 100% cotton archival photo paper, which is thick enough to survive the trip and feels like a proper postcard in your hand.
Designing for 4 × 6: quick tips
- Set up your file at 1200 × 1800 px (4 × 6 in at 300 dpi) so it prints sharp
- Keep important stuff away from the edges. Leave about 3 mm (0.125 in) of margin
- Leave room on the back for the stamp and address. See how to address a postcard for the layout
Skip the measuring
With Mango Postal, the canvas is already 4 × 6. Upload your photos, move them around and write your message. We print it on 100% cotton archival photo paper and mail it anywhere in Canada or the US for $4.99 CAD + $0.99 shipping.
FAQ
What is the standard postcard size in inches?
4 × 6 inches. That's 101 × 152 mm.
Is A6 a postcard size?
Yes. A6 (105 × 148 mm) is the common postcard size in Europe. It's very close to 4 × 6.
Is 5 × 7 a postcard?
It's often called one, but in the US it mails at the letter rate because it's larger than 4.25 × 6 in. In Canada it's within standard-size limits.
What size are Mango Postal postcards?
4 × 6 inches (101 × 152 mm), printed on 500 gsm, 100% cotton archival photo paper.
What's the largest postcard size before postage goes up?
In the US, 4.25 × 6 in. Anything larger mails at the letter rate ($0.82 instead of $0.65). Canada has no separate postcard rate: any card up to 245 × 156 mm (235 × 120 mm to the US or abroad) and 30 g pays the standard letter rate. See how much is a postcard stamp.
Make one now
Design a postcard on your phone. We print it and mail it anywhere in Canada or the US.
Build Postcard