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EDDM Mailpiece Size Requirements

USPS EDDM mailpiece requirements explained: EDDM Retail must be a flat, ≤ 3.3 oz, and exceed specific size thresholds. Use the USPS size checker to confirm compliance.

Nathan Crank·Founder, Postmarkr
EDDMUSPS

EDDM Mailpiece Size Requirements (2026)#

EDDM is amazing until your drop-off gets rejected because your postcard isn’t actually EDDM‑eligible.

USPS gives the requirements directly inside the EDDM Online Tool, including a Retail Mailpiece Size Checker. Source: USPS EDDM Online Tool. (https://eddm.usps.com/eddm/select-routes.htm)

This guide focuses on EDDM Retail requirements because that’s what most small and mid-sized local businesses use.

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The core EDDM Retail requirements (from USPS)#

USPS states that an EDDM Retail mailpiece must:

  • be a flat
  • weigh no more than 3.3 oz
  • and meet at least one of the following size conditions:

1) length greater than 10.5", or 2) height greater than 6.125", or 3) thickness greater than 0.25"

  • and also stay within USPS minimum and maximum dimensions for each side.

Source: USPS EDDM tool “Retail Mailpiece Size Checker.” (https://eddm.usps.com/eddm/select-routes.htm)

Translation: If your piece is small like a standard postcard, it may not qualify for EDDM Retail unless it clears those thresholds.

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What counts as a “flat” for EDDM?#

EDDM Retail requires a flat-sized mailpiece (not a letter).

In practice, most EDDM campaigns use:

  • oversized postcards (common)
  • folded self-mailers
  • flat flyers

If your piece is rigid, lumpy, or doesn’t behave like a flat, you’re increasing the chance of problems at acceptance.

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How to check your piece (the right way)#

Use USPS’s built‑in checker: 1) Go to the EDDM tool 2) Open the Retail Mailpiece Size Checker 3) Enter your piece dimensions and weight 4) Confirm it passes before printing

Source: USPS EDDM tool (Size Checker). (https://eddm.usps.com/eddm/select-routes.htm)

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Common sizing mistakes#

“My piece is 6×9.”#

This often fails EDDM Retail because it doesn’t exceed length 10.5", height 6.125", or thickness 0.25".

“It’s 11×6, so I’m good.”#

Careful: USPS requires greater than 10.5" length OR greater than 6.125" height. Being *exactly* at the threshold might not qualify depending on rounding and how it’s measured. Make it comfortably over.

“I’m under 3.3 oz… barely.”#

Paper stock and coatings can push you over. If you’re close, weigh a final printed sample.

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Related EDDM guides#

  • USPS EDDM Tool Step-by-Step: /blog/usps-eddm-online-tool-guide
  • EDDM Retail vs BMEU: /blog/eddm-retail-vs-bmeu
  • EDDM Postage Rates 2026: /blog/eddm-postage-rates-2026