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September 28, 2026 · 2 min read · The WCDMP print team

Which Postcard Sizes Qualify for EDDM (and Which Don't)

To mail with Every Door Direct Mail, your piece must be a USPS flat: longer than 10.5″, or taller than 6.125″, or thicker than 0.25″, and no larger than 15″ × 12″. That means a standard 4″ × 6″ postcard does not qualify, while sizes like 6″ × 11″, 6.5″ × 9″ and 4.25″ × 11″ do.

What is the EDDM size rule, exactly?

A piece counts as a flat if it meets at least one of these, and none of the maximums:

  • Length over 10.5″
  • Height over 6.125″
  • Thickness over 0.25″
  • Maximum 15″ long by 12″ high, and no thicker than 0.75″

Postcards are thin, so in practice they qualify on length or height.

Which of our postcard sizes qualify?

Postcard sizeEDDM?Why
4″ × 6″NoNeither side is long or tall enough
4.25″ × 6″NoNeither side is long or tall enough
3.5″ × 8.5″No8.5″ is under 10.5″
4″ × 9″No9″ is under 10.5″
5.5″ × 8.5″NoJust short on both sides
4.25″ × 11″Yes11″ is over 10.5″
6.5″ × 9″Yes6.5″ is over 6.125″
6″ × 11″Yes11″ is over 10.5″
8.5″ × 11″YesBoth sides clear the rule
9″ × 12″YesBoth sides clear the rule

What are the most common sizing mistakes?

Ordering 4″ × 6″ for EDDM. It is the most common postcard size and the least expensive (2,500 for $179), but it cannot go through EDDM. It is ideal for handing out, counter displays and addressed First-Class mail.

Choosing 5.5″ × 8.5″ because it "looks big enough." It is a popular size and priced the same as our slim 4.25″ × 11″ ($309 for 2,500), but only the 4.25″ × 11″ qualifies. If you want that price point for EDDM, choose the 4.25″ × 11″.

Assuming door hangers can be mailed. Door hangers are delivered by hand. Federal law does not allow anything without postage to be placed in a mailbox, so hang them on the door.

Which EDDM size should you choose?

  • 4.25″ × 11″: the least expensive EDDM postcard. Good for one offer, a coupon or a menu highlight.
  • 6.5″ × 9″: room for a photo and one clear offer, at a mid-range price.
  • 6″ × 11″: a wide card that stands out in the mailbox, with space for a photo, offer and map.
  • 8.5″ × 11″ and 9″ × 12″: full-page impact for several offers, listings or before-and-after photos.

Every size page on our postcards page shows whether it qualifies, and the EDDM comparison table puts all the eligible options side by side with prices.

Not sure which size fits your offer and budget? Call 512-573-1977, 7 days a week, and we'll recommend a size that qualifies before you order.

Talk to a print specialist, not a form.

Tell us what you're mailing and to whom. We'll price it, suggest the right size and help you pick EDDM routes, free. 7am–7pm ET, 7 days a week.

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