EDDM size requirements straight from the USPS rulebook: min and max dimensions, thickness, weight, folding, and a chart of which common sizes qualify and why.
You design a slick 6x9 card, print a few thousand, and find out at the Post Office counter that it doesn't qualify for EDDM Retail. Ouch. The EDDM size requirements are honestly simple, but plenty of pages quote numbers from the wrong part of the USPS rulebook. So here's the actual rule, every common size checked against it, and why the 9x12 we mail every month isn't technically a postcard at all.
Here's the thing. For EDDM Retail (the version you drop off at the Post Office yourself, no permit needed), USPS says a flat must weigh no more than 3.3 ounces and must be longer than 10.5 inches, OR taller than 6.125 inches, OR thicker than 0.25 inch (DMM 143.2.5). Pass one of the three and you're in. You don't need all three.
Over 10.5 in
Length test
Over 6.125 in
Height test
Over 0.25 in
Thickness test
Any 1 of 3
Tests you must pass
15 x 12 in
Maximum size
3.3 oz
Maximum weight
Two words do all the work: "greater than." A card exactly 10.5 inches long fails the length test. A card exactly 6.125 inches high (that's 6-1/8) fails the height test. Close doesn't count.
And length is always the longest side. USPS defines the length of a flat as its longest dimension, and the height as the dimension perpendicular to it (DMM 101.2.2). So a 9x12 is 12 inches long and 9 inches high, whether you design it landscape or portrait. New to EDDM? Start with how EDDM works and come right back.
The size test gets all the attention, but the full set of EDDM dimensions has a few more lines. Here's all of it, with the USPS source for each (Quick Service Guide 140 puts most of it on one page).
Spec
EDDM Retail rule
USPS source
Smallest piece
5 in long, 3.5 in high, 0.007 in thick
QSG 140
Size test
Over 10.5 in long, over 6.125 in high, or over 0.25 in thick
DMM 143.2.5
Largest piece
15 in long, 12 in high, 0.75 in thick
QSG 140
Weight
3.3 ounces max
DMM 143.2.5
Shape
Rectangular, with square corners or rounded corners up to 1/8 in radius
DMM 101.2.1
Flexibility
It has to bend. Boxes aren't flats
DMM 101.2.3
Even thickness
Bumps can't vary the thickness by more than 0.25 in
DMM 101.2.4
A few notes on the lines people skip:
Thickness. 0.007 inch is about three sheets of copy paper, per the USPS EDDM User Guide. Our 14 pt cards are 0.014 inch, twice the minimum.
Weight. Single-sheet cards rarely get close. Weigh one finished piece anyway, because the EDDM postage statement (PS Form 3587) asks for the weight of a single piece.
Over 3.3 ounces? Then it isn't EDDM Retail. Heavier pieces go through a Business Mail Entry Unit with a mailing permit.
Okay so here are the common EDDM sizes printers sell, plus the ones people ask me about, run through the rule. Short side first, all in inches.
Size (inches)
EDDM Retail?
Why
4 x 6
No
Fails all three tests. This is First-Class postcard territory
5.5 x 8.5
No
8.5 long, 5.5 high. Fails all three
6 x 9
No
9 isn't over 10.5, and 6 isn't over 6.125
6.125 x 9
No
Exactly 6.125 high isn't "greater than"
6.25 x 9
Yes
Height: 6.25 beats 6.125
6.5 x 9
Yes
Height. USPS lists it as a popular size
6 x 10.5
No
Exactly 10.5 long isn't "greater than"
4.25 x 11
Yes
Length: 11 beats 10.5
6 x 11
Yes
Length. This is our community card
6.5 x 11
Yes
Length and height
8.5 x 11
Yes
Length and height
9 x 12
Yes
Length and height. This is our 9x12 card
12 x 15
Yes
The maximum size allowed
11 x 17, flat
No
17 long is over the 15-inch maximum
11 x 17, folded to 8.5 x 11
Yes
Measured folded, it's an 8.5 x 11
USPS's own EDDM Retail fact sheet names 6.5 x 9, 8.5 x 11, and tri-fold menus at 4.25 x 14 as popular options. And every "yes" still has to weigh 3.3 ounces or less.
Orientation doesn't change whether a piece qualifies, because USPS measures length on the longest side however your art is laid out (DMM 101.2.2). It does change where the mailing block goes. USPS's EDDM Quick Reference sheet says the entire mailing block has to sit in the top half of the piece, and it can run along the long side or the short side, as long as it isn't upside down. The EDDM Retail indicia goes above and to the right of the "Postal Customer" line (DMM 144.1.3).
Joshua in our community built a vertical 9x12 for 10,000 homes, plus 5,000 flyers at 8.5 x 11. Portrait works fine. Just plan the mailing block before you place ads.
Folding is allowed. That same USPS fact sheet lists tri-fold menus as a popular EDDM size. Two rules to remember:
Measure it folded. The size test applies to the piece as it's mailed. An 11 x 17 sheet is too long flat (17 is over the 15-inch max), but folded in half it's an 8.5 x 11 and passes.
Keep it even. Flats have to be uniformly thick, so folds, inserts, or bulges can't vary the thickness by more than 0.25 inch (DMM 101.2.4). The folded piece also still has to bend and stay at 3.3 ounces or less.
If you searched for the EDDM postcard size, here's the twist: in USPS terms, no EDDM Retail piece is a postcard.
To USPS, a postcard is a card that qualifies for First-Class Mail card prices: at least 3.5 x 5 inches, no bigger than 4.25 x 6 inches, and 0.007 to 0.016 inch thick (DMM 101.6.2.2). Anything bigger is a letter or a flat, and the USPS user guide says EDDM Retail is limited to flats. So the moment a card is big enough for EDDM Retail, it's too big to be a USPS postcard. Our 9x12 card is a flat. So is the 6x11 community card.
Does the name matter? In conversation, no. Even the USPS EDDM page says "EDDM flyers, postcards, and other flats." On the printed piece, yes. USPS rules say a card that doesn't meet the postcard standards must not bear the word "Postcard" (DMM 101.6.2.3). So keep "Postcard" and "Jumbo Postcard" off the card itself.
Call it a postcard when you sell it. Leave the word off when you print it.
Look, I get why this is confusing. The general USPS definition of a flat in DMM 101.2.1 uses a longer length cutoff for regular mail. But that same line says "except as allowed for EDDM-Retail flats under 140," and section 143 sets the EDDM Retail test at more than 10.5 inches. Pages that copy the general number tell you a 6x11 won't work. It does, on length, and our members mail them all the time.
The other mix-up I see all the time: "9x12 is as big as EDDM goes." Nope. The ceiling is 15 inches long by 12 high, and a 9x12 sits comfortably inside it.
So when any page gives you an EDDM size number, check which DMM section it came from. If it isn't 143, it isn't the EDDM Retail rule.
For a solo mailer for your own business, any "yes" from the chart works. EDDM Retail postage is $0.26 per piece as of July 12, 2026, one price for any qualifying flat up to 3.3 ounces (Notice 123). So a bigger card costs more to print, not more to mail.
For a shared card, size is your inventory. Every square inch is ad space you sell. That's why we run two sizes:
Length and height
9x12 card passes on
About 16
9x12 ad slots
Length
Community card (6x11) passes on
About 16
Community card ad slots
The 9x12 card goes to 5,000 homes with about 16 slots at $500 each. The 6x11 community card goes to 2,500 homes with about 16 slots, typically around $250. Not sure which to start with? Here's what a community card is and why most beginners start there.
Size was never Lucy's problem, either. Her first community card was a 6.5 x 11, and her Amish butcher advertiser got six phone calls the day it landed. The hard part is selling slots, not picking dimensions.
With 9x12 Method Printing, you build on a plain 9x12 or 6x11 file and the print team adds the bleed. Our free 9x12 template shows where the mailing block sits, and the 9x12 print specs guide covers file setup. All Inclusive is $2,999 for a 9x12 to 5,000 homes or $1,449 for a community card to 2,500 homes, printed on 14 pt UV gloss with postage, bundling, and the Post Office drop handled. Going Print Only? Then the mailing is on you, and the EDDM drop-off checklist walks you through it.
Full transparency. I teach sizes, layouts, and the whole mailing process inside the 9x12 Method community, but you don't need it to get the size right. The rule fits in one sentence.
For EDDM Retail, a piece must be longer than 10.5 inches, taller than 6.125 inches, or thicker than 0.25 inch, and no bigger than 15 x 12 x 0.75 inches at 3.3 ounces or less. Sizes that pass include 6.25 x 9, 6 x 11, 8.5 x 11, and 9 x 12.
No. A 6x9 is 9 inches long and 6 inches high, which misses both the 10.5-inch length test and the 6.125-inch height test. A 6.25 x 9 passes on height, and a 6 x 11 passes on length.
15 inches long, 12 inches high, and 0.75 inch thick, at no more than 3.3 ounces. Anything longer than 15 inches, like a flat 11 x 17, is too big unless it's folded down.
Yes. USPS's EDDM Retail fact sheet lists tri-fold menus as a popular size. Measure the piece folded, keep it uniformly thick (no more than 0.25 inch of variance), and keep it at 3.3 ounces or less.
A flat. USPS postcards top out at 4.25 x 6 inches, so a 9x12 is mailed as a flat, which is all EDDM Retail accepts. USPS rules also say a card that isn't a USPS postcard must not bear the word "Postcard," so leave it off the printed piece.
At least 0.007 inch, about three sheets of copy paper, and no more than 0.75 inch. A piece thicker than 0.25 inch passes the size test on thickness alone. 14 pt cardstock is 0.014 inch, twice the minimum.
Look, the whole size rule fits on a sticky note. Pass one test, stay under the ceiling, keep it at 3.3 ounces or less, and leave "Postcard" off the card. Then spend your energy on what actually matters: filling the thing.
As always, I'm rooting for you. Peace.
Ready to run your own card?
Get the course, scripts, tools, and weekly coaching inside the 9x12 Method community.
Mitchell Tebo
