The single most common reason EDDM mailings get rejected at the post office counter is incorrect sizing. USPS requires EDDM mailpieces to meet specific dimensional standards to qualify as "Flats"—and the margins are precise. A postcard that measures 6 inches tall instead of 6.25 inches doesn't qualify, and you'll either face rejection or significantly higher postage.
For an end-to-end operational context, review USPS Every Door Direct Mail specifications alongside this format guide.
This guide covers every physical specification your EDDM mailpiece needs to meet, explains why these requirements exist, and helps you choose a format that works for your campaign.
Why Size Matters for EDDM#
For budget planning, see how format affects EDDM pricing in detail.
EDDM mailpieces must be classified as "Flats" under USPS processing standards. This isn't arbitrary—it determines how your mail moves through the postal system.
Standard letters (like a #10 envelope or a 4" × 6" postcard) are processed through high-speed automated sorting equipment. Flats are too large for this machinery, so they're processed separately and bundled for direct carrier delivery. EDDM specifically relies on this handling path: your pre-bundled mail goes directly to the carrier who delivers the routes you've selected.
If your mailpiece is too small to qualify as a Flat, it enters the letter-processing stream instead. At that point, it no longer meets EDDM requirements. The post office will either reject your mailing or charge you First-Class letter rates—roughly three times the EDDM postage cost.
Getting the dimensions right isn't optional. It's the difference between your campaign proceeding as planned and a very expensive mistake.
EDDM Dimensional Requirements#
To qualify as an EDDM Flat, your mailpiece must exceed at least one of the letter-size maximums. You don't need to exceed all three—just one.
Minimum Dimensions (Must Meet at Least One)#
| Dimension | Minimum to Qualify | |-----------|-------------------| | Height | Greater than 6.125 inches (6-1/8") | | Length | Greater than 10.5 inches | | Thickness | Greater than 0.25 inches (1/4") |
Height is measured perpendicular to the length (the shorter side on a typical postcard). Length is measured parallel to the address line (the longer side). Thickness applies to multi-panel pieces, booklets, or anything with substantial bulk.
The critical detail: these are "greater than" thresholds, not "equal to." A mailpiece that is exactly 6.125 inches tall does not qualify. It must be 6.126 inches or more. In practice, this means designing to at least 6.25 inches tall to provide a comfortable margin for printing and trimming variation.
Maximum Dimensions#
| Dimension | Maximum Allowed | |-----------|-----------------| | Height | 12 inches | | Length | 15 inches | | Thickness | 0.75 inches (3/4") |
The maximum dimensions define the largest Flat the USPS will accept for EDDM. Anything larger gets classified as a parcel and priced accordingly.
Weight Limit#
Maximum weight: 3.3 ounces per piece
This limit applies to EDDM Retail. Most standard postcard formats on typical cardstock come in well under this threshold—a 6.5" × 9" piece on 14pt stock weighs approximately 0.8 ounces. You'd need very heavy paper or an unusually large format to approach the limit.
If you're designing a multi-panel piece, thick brochure, or using premium paper stock, verify the finished weight before production. Exceeding 3.3 ounces disqualifies the piece from EDDM Retail rates.
Common EDDM Postcard Sizes#
Printers have standardized around several formats that efficiently use standard paper sheet sizes while meeting EDDM requirements. These are your safest choices:
6.5" × 9" (Most Popular)#
This is the workhorse EDDM format. It qualifies as a Flat because the 6.5" height exceeds the 6.125" minimum. It's large enough to be noticed but small enough to print economically.
Works well for: General promotional offers, service announcements, grand openings, single-message campaigns.
8.5" × 11" (Letter Size)#
The dimensions of a standard sheet of paper. This format offers substantially more design space than a postcard and can accommodate detailed content like menus, service lists, or maps.
Works well for: Restaurant menus, real estate market updates, detailed service catalogs, event announcements with schedules.
9" × 12"#
A large-format postcard that commands significant mailbox presence. This size is often used when visual impact is a priority and the business can support the higher printing cost.
Works well for: Real estate "Just Sold" announcements, high-end service providers, grand opening splash campaigns.
6.25" × 11" or 6.5" × 11"#
A longer, narrower format that qualifies on both height and length dimensions. The elongated shape stands out visually and can work well for horizontal layouts.
Works well for: Before/after comparisons, timeline presentations, services displayed as a horizontal flow.
11" × 17" (Folded)#
This format starts as a large sheet and folds to a finished size of 8.5" × 11" or similar. It offers four panels of content space—useful when you have extensive information to communicate.
Works well for: Detailed menus, product catalogs, real estate neighborhood guides, nonprofit appeal letters with donation forms.
12" × 15" (Maximum Size)#
Sometimes called the "mega mailer," this is the largest format EDDM allows. It physically dominates the mailbox and ensures visibility. The tradeoff is significantly higher printing costs.
Works well for: Market entry campaigns where maximum visibility justifies the cost, luxury brands, competitive categories where standing out is critical.
Sizes That Do NOT Qualify for EDDM#
Several common formats fall below EDDM dimensional requirements:
| Size | Why It Doesn't Qualify | |------|------------------------| | 4" × 6" postcard | Too small in all dimensions | | 5" × 7" postcard | Height (5") and length (7") both under minimums | | 6" × 9" postcard | Height (6") is at or below the 6.125" minimum | | #10 envelope | Standard letter dimensions, not a Flat | | 5.5" × 8.5" (half letter) | Both dimensions under minimums |
The most frequent mistake is assuming a "jumbo" 6" × 9" postcard qualifies. It doesn't. That fraction of an inch—6" versus 6.25"—is the difference between EDDM pricing and a rejected mailing.
If your printer offers 6" × 9" as an EDDM option, clarify the exact finished dimensions. Some printers use "6 × 9" loosely to describe a 6.5" × 9" piece. Others mean exactly 6" × 9", which does not qualify.
Paper Weight and Stiffness#
While USPS doesn't mandate a specific paper weight for EDDM, practical considerations and quality perceptions influence the right choice for your campaign.
Minimum Thickness Requirement#
USPS requires Flats to be at least 0.007 inches thick. Most cardstock exceeds this easily. However, standard copy paper (20 lb bond) may not meet the threshold, particularly for single-sheet pieces without folding.
Recommended Paper Weights#
| Stock | Typical Use | Notes | |-------|-------------|-------| | 80 lb gloss cover (~10pt) | Budget campaigns | Acceptable but may feel flimsy | | 100 lb gloss cover (~12pt) | Standard mailings | Good balance of cost and feel | | 120 lb gloss cover (~14pt) | Most EDDM campaigns | Industry standard, sturdy feel | | 130 lb gloss cover (~16pt) | Premium feel | Higher cost, noticeably thick |
14pt gloss cardstock has become the de facto standard for EDDM postcards. It's thick enough to feel substantial when handled, rigid enough to resist bending in the mailbox, and priced reasonably at most print vendors.
Thinner stocks (10-12pt) can feel cheap to recipients, potentially undermining your brand impression. Thicker stocks (16pt+) add print cost without dramatically improving response rates for most campaigns.
Flexibility Requirements#
EDDM Flats must be flexible—bendable without breaking or cracking. This rules out rigid materials like chipboard, mounted prints, or laminated pieces that don't flex.
The practical test: your mailpiece should be able to curve gently when held at opposite edges without cracking, creasing, or breaking. Standard cardstock passes easily; certain rigid specialty materials may not.
Indicia and Address Placement Rules#
Compliance checks are summarized in our EDDM requirements checklist.
Beyond dimensions, EDDM mailpieces must follow specific layout requirements for the indicia (the "stamp" area) and address block.
The "Top Half" Rule#
The delivery address and indicia must appear in the top half of the mailpiece, as measured from the shorter dimension. On a 6.5" × 9" postcard oriented horizontally (address on the 9" side), the top half is the upper 3.25 inches.
Everything required for postal processing—the indicia, the "Local Postal Customer" address line, and your return address—must fit within this zone.
Indicia Placement#
The EDDM indicia goes in the upper right corner of the address side. For EDDM Retail, the indicia must read "EDDM Retail" in the final line. Your printer should have the correct indicia format; verify before production that they're using the Retail version and not a permit indicia (which requires a permit you may not have).
Address Format#
EDDM pieces are not addressed to specific recipients. Instead, the address line reads one of these approved formats:
Local Postal Customer
Postal Customer
Residential Customer
This line goes in the standard address position: below center on the right side of the mailpiece, within the top half.
Return Address#
A return address is required on all EDDM pieces. It typically appears in the upper left corner of the address side. Include your business name, street address, city, state, and ZIP code.
Note that undeliverable EDDM mail is typically discarded rather than returned to you (unlike First-Class mail), but the return address is still mandatory.
Clear Zone#
Maintain a clear zone around the address area—free from graphics, heavy ink coverage, or text—to ensure postal processing equipment can read the address. The barcode clear zone is a rectangle approximately 4.75" wide by 0.625" tall at the bottom of the address side.
Design Layout Best Practices#
Format constraints are easier to evaluate when compared with EDDM vs traditional direct mail.
With dimensional requirements understood, here are practical guidelines for laying out your EDDM design:
Design for 6.5" × 9" minimum. Even if your concept would work at 6" × 9", add the extra half-inch to ensure qualification. The printing cost difference is negligible; the risk of rejection is not.
Build in trim tolerance. Commercial printing involves cutting large sheets down to finished size. If your design extends to the exact edge (full bleed), add 0.125" bleed on all sides and keep critical content at least 0.25" from trim edges. A design that technically meets 6.5" height could trim to 6.4" if cut slightly off—below the threshold.
Separate address side from creative side. Most EDDM postcards use one side for the promotional message and the opposite side for addressing/indicia. This simplifies compliance—all postal requirements live on one side while your marketing has uninterrupted space on the other.
Proof at actual size. Before approving a print run, print a proof at 100% scale and physically measure it. Verify it exceeds 6.125" height (or whatever dimension you're qualifying on). A few minutes of verification prevents a costly production error.
Frequently Asked Questions#
Can I use a 6" × 9" postcard for EDDM?#
No. A 6" tall mailpiece does not meet the minimum height requirement of greater than 6.125 inches. Use 6.5" × 9" instead, which qualifies because 6.5" exceeds the threshold.
Does paper weight affect EDDM eligibility?#
Not directly, as long as the finished piece meets the minimum 0.007" thickness. However, heavier paper increases total weight—if your piece exceeds 3.3 ounces, it no longer qualifies for EDDM Retail rates.
Can I mail a folded piece?#
Yes. Folded brochures, menus, and multi-panel pieces qualify for EDDM as long as the finished (folded) dimensions meet the Flat requirements and the piece doesn't exceed 3.3 ounces. The fold must be secure—pieces that might unfold during processing can be rejected.
What happens if my mailpiece is slightly under the size requirement?#
The post office will either reject your mailing or process it as letter mail at significantly higher postage (roughly $0.78 per piece instead of $0.247). Neither outcome is acceptable. Always design with margin above the minimums.
Can I include inserts or attachments?#
Loose inserts are generally not permitted—everything must be a single integrated piece. Items that could fall out during processing will be rejected. If you want to include a coupon or response card, it must be attached (perforated, glued, or printed as part of the piece).
Is there a minimum thickness for EDDM?#
Yes, 0.007 inches minimum. Standard cardstock (10pt and above) exceeds this easily. Single sheets of standard copy paper may not qualify.
Size Checklist Before Printing#
Before approving your EDDM print run, verify:
[ ] Finished height is greater than 6.125" OR finished length is greater than 10.5" OR thickness is greater than 0.25"
[ ] Finished dimensions do not exceed 12" × 15" × 0.75"
[ ] Finished weight is under 3.3 ounces
[ ] Paper stock is at least 0.007" thick and flexible
[ ] Indicia and address block are in the top half of the mailpiece
[ ] Return address is included
[ ] Design includes bleed and safe margins for trim tolerance
[ ] Printer confirms these are EDDM-compliant dimensions
For a comprehensive pre-flight checklist covering all EDDM requirements, see our EDDM requirements checklist.
Official USPS Resources: