Postcard Sizes & Dimensions Guide (Updated May 2026)
Quick answer: The most common standard postcard sizes are 4" × 6", 5" × 7", 8.5" × 5.5", 6" × 9", and 6" × 11". Only cards from 3.5" × 5" up to 4.25" × 6" qualify for the low USPS postcard stamp rate — anything bigger is billed as a letter or Marketing Mail. Below is every size with its exact dimensions, the postage class it qualifies for, whether it works for EDDM, and what we'd use it for here at Catdi Printing in Houston.
Last updated: May 2026.
Standard Postcard Sizes at a Glance
If you only read one thing, read this table. These are the five sizes we print most often, with the dimensions and the postage rate each one actually qualifies for.
| Size | Dimensions | Postage class it qualifies for | EDDM-eligible? | Best use |
|---|---|---|---|---|
| 4" × 6" | 4" × 6" | USPS postcard rate (lowest) | No | Mass direct mail, handouts, reminders |
| 5" × 7" | 5" × 7" | First-Class letter / Marketing Mail | No | Invitations, announcements, offers |
| 8.5" × 5.5" | 8.5" × 5.5" | First-Class letter / Marketing Mail | No | Roomy standard mailer, menus, coupons |
| 6" × 9" | 6" × 9" | First-Class letter / Marketing Mail | Yes | High-impact campaigns, EDDM saturation |
| 6" × 11" | 6" × 11" | First-Class letter / Marketing Mail | Yes | Maximum mailbox impact, EDDM drops |
Postage class depends on final size, thickness, and aspect ratio. Always confirm current pricing on the official USPS postage prices page before printing.
The 4.25" × 6" Postcard-Rate Threshold
This is the single most important number in postcard mailing, and it's the one most people miss. USPS gives a discounted postcard stamp rate only to cards that fall between 3.5" × 5" and 4.25" × 6". Go a hair over that — even by an eighth of an inch — and your "postcard" is mailed at the First-Class letter rate instead.
In 2026, that postcard stamp is $0.61 (a proposed increase to $0.65 is pending Postal Regulatory Commission approval, effective July 12, 2026), per the official USPS 2026 price change notice. Here is what the threshold means in practice:
- 4" × 6" fits inside the window → qualifies for the low postcard rate.
- 5" × 7", 8.5" × 5.5", 6" × 9", and 6" × 11" all exceed 4.25" × 6" → mailed at letter or Marketing Mail rates.
That doesn't make the bigger sizes "bad" — it just means you trade a little postage for a lot more presence. For a full cost-versus-impact breakdown, read our guide to standard vs. oversized postcards, and see the full rate picture in our postage & mailing costs guide.
Verify final postage before you print. Thickness, aspect ratio, and an extra eighth of an inch can bump a postcard into a higher rate. At Catdi we confirm the exact postage for your piece before anything goes on press — so the number you budget is the number you pay.
A Closer Look at Each Standard Size
4" × 6" — The Cost King
The original workhorse. At exactly 4" × 6", this is the only common size that earns the discounted USPS postcard rate, which makes it the cheapest card to mail at scale. It fits standard mail slots, is easy to hand out at events, and is perfect for appointment reminders, quick promos, and high-volume sends.
- Qualifies for the lowest First-Class postcard postage.
- Ideal for mass mailings where budget matters most.
- Compact and easy to distribute by hand.
5" × 7" — The Balanced Choice
At 5" × 7", you get noticeably more design room without going jumbo. It stands taller in a stack of mail and reads as a premium piece, which makes it a favorite for invitations, announcements, and promotional offers. It exceeds the 4.25" × 6" window, so it mails at letter/Marketing Mail rates.
8.5" × 5.5" — The Roomy Standard
Half of a letter sheet, 8.5" × 5.5" is a wide, generous mailer with strong shelf presence. It gives you space for a coupon, a menu, or a detailed offer while still feeling tidy. Like the others above 4.25" × 6", it's billed at letter/Marketing Mail rates.
6" × 9" — The Oversized Workhorse
The 6" × 9" is where direct mail starts to dominate the mailbox. It's big enough for detailed graphics and a clear call-to-action, and it's EDDM-eligible, so you can saturate neighborhoods without buying a mailing list. A top pick for high-impact campaigns.
6" × 11" — Maximum Impact
The 6" × 11" is our biggest standard mailer and a top EDDM format. There's room for comprehensive information, bold imagery, and an unmissable offer. When you want to own the mailbox and reach every door in an area, this is the size. See eligible formats on our EDDM postcard sizes page and learn how saturation mailing works on our full-service EDDM page.
What About Custom & Square Postcards?
Standard sizes aren't your only option. Custom dimensions let you stand out — just keep two things in mind:
- Stay USPS-compliant. Odd shapes and squares can trigger non-machinable surcharges or get kicked to manual sorting, which raises postage.
- Square cards are great for handouts, less ideal for mail. They look striking in person but often cost more to send.
If you're unsure, we'll help you pick a size that hits your design goals without surprising you at the post office.
Which Size Should You Mail? Quick Picks by Goal
The "best" postcard size is the one that fits your message, your audience, and your budget. Here is how we steer customers when they ask — matched to what they are actually trying to do:
- 4×6 — reminders & high-frequency mailings. Appointment reminders, simple offers, or any campaign you repeat monthly. The lowest First-Class postage stretches your budget across more touches.
- 5×7 — promotions & invitations. A noticeable step up in presence for sales, events, and grand openings, without going oversized.
- 8.5×5.5 — detailed offers & mini-menus. Half-page room for multiple offers, a coupon block, or a short menu.
- 6×9 — standing out & real estate. The oversized workhorse: dominates the mailbox, EDDM-eligible, and on a bulk drop it mails at the same postage as a smaller card.
- 6×11 — maximum impact & EDDM saturation. The biggest common format and a top EDDM size when being seen first is worth it.
Running EDDM or not sure which way to go? Compare the trade-offs in our standard vs. oversized postcards guide, or get a real number on our direct mail calculator.
How to Choose the Right Postcard Size
- Start with the goal. Reminders and high-volume sends → 4" × 6". Big announcements and saturation → 6" × 9" or 6" × 11".
- Mind the 4.25" × 6" threshold. Only 4" × 6" gets the cheap postcard stamp; bigger cards mail at letter/Marketing Mail rates.
- Check EDDM eligibility. For neighborhood saturation without a list, choose an EDDM-eligible size like 6" × 9" or 6" × 11".
- Balance impact vs. budget. A bigger card costs a bit more to mail but commands far more attention — decide which matters more for this campaign.
- Confirm postage before you print. We estimate exact postage for your final piece so there are no surprises.
Size & postage — the part to get right: on Standard / Marketing Mail (what most bulk postcard campaigns use), all of these sizes mail as "letters" at the same postage — a 6×9 costs the same to mail as a 4×6. Size only changes postage on First-Class, where only a card up to 4.25" × 6" earns the low postcard rate. On a bulk drop, going bigger for impact usually costs nothing extra; what drives Standard-rate cost is weight and address density.
Postcard Sizes FAQ
What is the standard postcard size?
The most common standard postcard size is 4" × 6". Other popular standards are 5" × 7", 8.5" × 5.5", 6" × 9", and 6" × 11". Only cards up to 4.25" × 6" qualify for the low USPS postcard rate.
What size postcard qualifies for the USPS postcard rate?
USPS applies the discounted postcard stamp rate only to cards from 3.5" × 5" up to 4.25" × 6". Anything larger is billed at First-Class letter or Marketing Mail rates. Confirm current pricing on USPS.com.
What are the dimensions of a 6x9 postcard?
A 6" × 9" postcard measures exactly six inches by nine inches. It's EDDM-eligible and mails at letter/Marketing Mail rates because it exceeds the 4.25" × 6" postcard-rate threshold.
Which postcard sizes are EDDM-eligible?
Larger formats like 6" × 9" and 6" × 11" work well for Every Door Direct Mail. See the complete list on our EDDM postcard sizes page.
Does a bigger postcard cost more to mail?
Usually, yes. Only 4" × 6" gets the low postcard rate; 5" × 7", 8.5" × 5.5", 6" × 9", and 6" × 11" mail at letter or Marketing Mail rates. The extra postage buys more mailbox impact — see our standard vs. oversized guide.
Can I print a custom-size postcard?
Absolutely. Custom and square cards are great for handouts and standout campaigns, but keep them USPS-compliant for mailing to avoid non-machinable surcharges. We'll help you choose a size that fits your goals and your postage budget.
Ready to Print Your Postcards?
Catdi Printing prints postcards in every standard size — 4" × 6" through 6" × 11" — and we confirm your real postage before you commit. Browse postcard printing options, compare formats in our standard vs. oversized guide, or request a free, itemized quote with postage included. Prefer to talk it through? Call us at (713) 882-4629.