Not every postcard is a "postcard"
USPS has a specific definition, and it matters for postage. To mail at the First-Class postcard price a card must be:
| Minimum | Maximum | |
|---|---|---|
| Height | 3.5 in | 4.25 in |
| Length | 5 in | 6 in |
| Thickness | 0.007 in | 0.016 in |
Anything larger is still a card you can mail, but it pays letter or flat prices instead, and USPS says it shouldn't carry the word "Postcard".
The three size families
| Family | Typical sizes | Mails as | Notes |
|---|---|---|---|
| Standard | 4 x 6 | Postcard | Cheapest First-Class postage, least room |
| Letter-size | 5.5 x 8.5, 6 x 9, 6 x 11 | Letter | Up to 6.125 x 11.5 in and 0.25 in thick |
| Flat-size | 6.5 x 9 and up to 12 x 15 | Flat | Used for EDDM, the most room |
Note the overlap. A 6 x 11 card fits within letter limits for addressed mail, and it also qualifies for EDDM Retail because it's longer than 10.5 inches.
Postage at a glance
| How it's sent | Price per piece |
|---|---|
| First-Class retail postcard (stamp) | $0.65 |
| First-Class presorted postcard, automation 5-digit | $0.453 |
| USPS Marketing Mail letter, saturation | $0.255 |
| EDDM Retail flat | $0.260 |
Presorted and Marketing Mail prices need a minimum quantity, sorting and a permit or postage method. A mail house usually handles that.
Picking a size
- Short reminder to existing customers: a standard postcard.
- Addressed offer to a list: a letter-size card such as 6 x 9 or 6 x 11. It has room for an offer and mails at letter prices.
- Every home in an area: a flat-size card that meets the EDDM rules, like 6.5 x 9 or 6 x 11.
Questions readers ask
What size is a USPS postcard?
At least 3.5 x 5 inches and no more than 4.25 x 6 inches, between 0.007 and 0.016 inches thick.
What does it cost to mail a postcard?
$0.65 with a First-Class postcard stamp. Presorted commercial postcards cost less.
Is a 6x9 card a postcard?
Not by USPS's definition. It mails at letter prices.