The 5 postcard sizes that qualify for EDDM
Five sizes work for EDDM Retail. Three popular postcard sizes don't. Here is how to pick the right one without wasting a print run.
This page is for anyone who picked a postcard size that looked right, then learned the printer cannot mail it under Every Door Direct Mail. By the end you will know the five sizes that qualify for EDDM Retail, the three popular sizes that fail the USPS rule, and how to choose between eligible options. For the full rulebook, the EDDM size guidelines pillar is the deeper reference.
The short answer: 5 sizes that qualify for EDDM
EDDM Retail requires the mailpiece to qualify as a USPS flat. To count as a flat, the piece must exceed at least one of: length greater than 11.5 inches, height greater than 6.125 inches, or thickness greater than 0.25 inches. Most postcards are not thick, so size is what matters. The five below all clear the bar.
- 6.5" x 9" — entry-level EDDM size, cheapest to print and mail.
- 6.5" x 11" — more room for an offer plus a map.
- 8.5" x 11" — menu and service-list territory.
- 9" x 12" — high impact, higher cost.
- 11" x 17" folded — newsletters and folded menus, only if the final folded dimensions still clear the flat threshold.
If your size is not on that list, assume it does not qualify and read the next section before sending it to print.
The 5 recommended EDDM sizes (comparison)
Here is the side-by-side view. "Best for" reflects what we actually see customers mail successfully; "tradeoff" names what you give up.
| Size | EDDM eligible | Best for | Tradeoff |
|---|---|---|---|
| 6.5" x 9" | Yes (height > 6.125") | First-time tests, restaurants, contractors, single-offer mailers | Less room for copy; can look small next to oversized pieces |
| 6.5" x 11" | Yes | Offer plus map, real estate, multi-product promos | About 15-25% more print cost than 6.5x9 |
| 8.5" x 11" | Yes | Menus, service lists, event mailers, dental and medical offices | Heavier stocks can push you toward the 3.3 oz cap; verify with your printer |
| 9" x 12" | Yes | Catalog-style offers, premium brands, real estate broker comps | Highest print cost of the five; not always justified if a smaller card fits the offer |
| 11" x 17" folded | Sometimes — only if the finished folded size still qualifies as a flat | Newsletters, multi-page menus, seasonal catalogs | Folded dimension math is easy to get wrong; confirm the finished size before approving the proof |
Postage on EDDM Retail is the same per piece regardless of size, currently $0.247 at USPS retail rates. The cost decision is really about printing, not mailing.
Rule of thumb: If you are testing EDDM for the first time, start with 6.5 x 9 at 2,500 to 5,000 pieces. It is the lowest-risk way to learn what your response rate looks like before committing to a larger format.
Sizes you will see online that do not actually qualify for EDDM
Three postcard sizes show up constantly in templates and stock-photo mockups, and none of them work for EDDM Retail. Knowing this up front saves a reprint.
| Size | Why it fails for EDDM |
|---|---|
| 4" x 6" | Length is 6", height is 4", thickness is well under 0.25". It clears none of the three flat thresholds. This is a standard first-class postcard size, not an EDDM size. |
| 5" x 7" | Same problem. Neither dimension exceeds 6.125" or 11.5", and a standard postcard is too thin to clear the 0.25" thickness rule. Pretty card, wrong category. |
| Standard 6" x 9" | This is the one that catches people. Length is exactly 9" (under 11.5") and height is exactly 6" (under 6.125"). It fails by 1/8 of an inch on the height. A 6.5" x 9" passes; a 6" x 9" does not. |
For the full USPS rule language and the exact thresholds, the EDDM size requirements page has the source text.
Why 6 x 9 is the most common mistake
The 6 x 9 postcard is the single most common size mistake we see, and it happens because every other postal category accepts it. A 6 x 9 is a standard first-class postcard and a standard size in design software templates. So it feels safe. For EDDM Retail, it is not.
A 6 x 9 has a length of 9" and a height of 6". Both are under the flat thresholds. USPS classifies it as a letter, and EDDM Retail does not accept letters.
The fix is straightforward: bump the height from 6" to 6.5". You get a 6.5" x 9" that clears the height threshold by 3/8 of an inch and qualifies as a flat. The design barely changes, the print cost barely changes, and the EDDM eligibility flips from "no" to "yes." If a vendor offers you a 6 x 9 for EDDM, ask them to confirm the dimensions in writing before you approve the proof.
How to choose between 6.5 x 9, 6.5 x 11, 8.5 x 11, and 9 x 12
Once you know all four sizes qualify, the choice comes down to message, budget, and what your neighbors are mailing.
- Pick 6.5 x 9 if you have one offer, one call-to-action, and a budget under roughly $0.50 per piece all-in. Most restaurants, salons, and HVAC contractors land here.
- Pick 6.5 x 11 if you need to show an offer and a map, or two offers side by side. Real estate agents and multi-location retailers tend to like this format.
- Pick 8.5 x 11 if your message is a menu, a service list, or an event flyer. The page-sized format reads like a document rather than an ad, which works in your favor for medical, dental, and educational mailers.
- Pick 9 x 12 if you want maximum visual presence in the mailbox and you have a premium offer that justifies the print cost. Diminishing returns kick in fast above this size.
If two sizes feel equally right, the smaller one usually wins on cost per response. Bigger is not always better — it is just bigger. For artwork rules at each size (bleed, safe zone, indicia placement), the EDDM design guidelines walk through the setup file by file.
Folded pieces: when 11 x 17 folded works
An 11 x 17 sheet folded in half becomes an 11 x 8.5 finished piece, which qualifies as an EDDM flat because the 11" length exceeds 11.5". Folded in thirds it becomes roughly 11 x 5.67, which fails because neither finished dimension clears the thresholds. Rule of thumb: check the finished dimensions, not the unfolded sheet.
Folded pieces also need to be tabbed or sealed — USPS will not accept loose-folded flats. Your printer should handle tabbing as part of the EDDM full-service workflow.
Frequently asked questions
Can I mail a 4 x 6 postcard with EDDM?
No. The 4 x 6 size does not qualify as a flat, so it cannot be mailed under EDDM Retail. You can mail a 4 x 6 as a first-class postcard with addresses on each piece, but that is a different product with different pricing and no route-level distribution.
Is a 6 x 9 ever acceptable for EDDM?
Almost never. The dimensions fall under both the 11.5" length threshold and the 6.125" height threshold, so USPS classifies it as a letter, not a flat. EDDM Retail requires flats. Use 6.5" x 9" instead — it is the closest size up and it clears the rule.
Does the postage change between 6.5 x 9 and 9 x 12?
No. EDDM Retail postage is a flat per-piece rate ($0.247 currently) regardless of which qualifying size you pick, as long as you stay under the 3.3 oz weight cap. The cost difference between sizes is print cost, not postage.
What about a 7 x 10 or other in-between size?
A 7 x 10 qualifies because the height (7") exceeds 6.125". Any custom size that exceeds at least one of the three flat thresholds and stays under the 15 x 12 x 0.75 maximum will qualify. The five we recommend simply have the best print economics on common stocks.
Pick a size and get a quote
If you already know which size you want, head to the EDDM quote page and choose your routes — the configurator will price print plus postage in one step. If you want a second opinion before committing, the EDDM size guidelines pillar covers the full decision in more depth, or call us at (713) 300-0687 and we will walk through the tradeoffs in five minutes.