Political Mailer Sizes: Postcards, Letters, Flats, and EDDM

Political mailer sizes fall into four USPS categories, and each one has hard limits: a postcard tops out at 4.25 by 6 inches, a letter at 6.125 by 11.5 inches, a flat at 12 by 15 inches, and an Every Door Direct Mail piece follows the flat maximums with a stricter weight cap. Exceed any single dimension in a category and the piece drops into the next pricing tier, where per-piece costs can climb sharply across a mailing of thousands.

Postcard Size Limits

Postcards qualify for the lowest postage rate of any mailpiece format, which is why high-volume campaigns lean on them. To get that rate, a piece must be rectangular and meet these limits:1United States Postal Service. Domestic Mail Manual 201 – Physical Standards

  • Minimum size of 3.5 inches high by 5 inches long
  • Maximum size of 4.25 inches high by 6 inches long
  • Thickness between 0.007 and 0.016 inch

The thickness range matters more than most campaigns realize. Below 0.007 inch, the piece is non-mailable entirely. Above 0.016 inch, it gets reclassified as a letter and costs more per piece. The stock has to be stiff enough for sorting machines to grip but thin enough to stay inside the card category. Most commercial printers know these tolerances, but confirm the cardstock thickness before approving a proof.

At current First-Class rates, a postcard stamp costs $0.61.2United States Postal Service. U.S. Postal Service Recommends New Prices for July Campaigns sending in bulk through a Marketing Mail permit pay considerably less per piece, which is where the real savings on large political mailings come from.

Letter-Size Mailers

Most political mailers land in the letter category. It covers the common 6-by-9 and 6-by-11 pieces that look like oversized postcards but are technically too large for the postcard rate. Letter-size maximums are:3United States Postal Service. Business Mail 101 – Sizes for Letters

  • Height up to 6.125 inches
  • Length up to 11.5 inches
  • Thickness up to 0.25 inch
  • Weight up to 3.5 ounces for First-Class4United States Postal Service. First-Class Mail

The overlooked trap is the aspect ratio. Divide length by height, and the result must land between 1.3 and 2.5.1United States Postal Service. Domestic Mail Manual 201 – Physical Standards A square mailer fails automatically, and so does anything with extreme proportions. Pieces outside that range take a $0.49 nonmachinable surcharge per piece because they require manual handling instead of running through automated sorting equipment.5United States Postal Service. USPS Notice 123 – January 2026 Price Change On a 50,000-piece run, that surcharge alone adds $24,500. Designers who lock in a creative concept before checking the aspect ratio math learn the lesson the expensive way.

Folded Self-Mailers

Folded self-mailers skip the envelope. A flat sheet folds down into a letter-size piece sealed with tabs, and the full exterior becomes printable space. USPS requires at least two tabs with no perforations, each at least one inch in size. Pieces weighing over one ounce need larger 1.5-inch tabs. Placement rules differ depending on whether the piece is a standard bi-fold, oblong fold, or quarter-fold, so check the specific folding style against USPS guidelines before committing to a design. A mailer that arrives at the post office without proper tabbing gets rejected.

Flats and Large Envelopes

When a piece exceeds any single letter-size dimension, it moves into the flat category. USPS uses “flat” and “large envelope” interchangeably. Common political formats in this tier include 9-by-12 envelopes and oversized newsletters. A flat must:6United States Postal Service. Business Mail 101 – Sizes for Large Envelopes and Flats

  • Exceed at least one letter dimension: taller than 6.125 inches, longer than 11.5 inches, or thicker than 0.25 inch
  • Stay within maximums of 12 inches high, 15 inches long, and 0.75 inch thick
  • Weigh less than 16 ounces7United States Postal Service. 240f Quick Service Guide

Flats also have to pass a flexibility test. The piece is extended halfway off a flat surface, and pressure is applied one inch from the outer edge. If it can’t bend at least one inch without damage, it’s too rigid and gets reclassified as a parcel. Pieces with rigid inserts face an additional test where each end must bend at least two inches when extended five inches off the surface. Parcel pricing roughly doubles the per-piece cost compared to flat pricing, so a thick campaign packet with a rigid bumper sticker or magnet inside can blow up a mailing budget. Keep the contents uniform in thickness and flexible enough to curve through automated sorting belts.

Every Door Direct Mail Sizes

Every Door Direct Mail lets campaigns blanket entire carrier routes without a mailing list or individual addresses. The piece goes to every household and business on the route. To qualify for EDDM Retail, the mailpiece must meet at least one of these minimum thresholds:8United States Postal Service. Domestic Mail Manual – USPS Marketing Mail Flats Every Door Direct Mail-Retail

  • Longer than 10.5 inches, or
  • Taller than 6.125 inches, or
  • Thicker than 0.25 inch

Meeting one trigger is enough. The maximums match standard flats at 15 inches long, 12 inches high, and 0.75 inch thick.9United States Postal Service. 140 Quick Service Guide – EDDM-Retail The weight cap is stricter than regular flats, though: EDDM Retail pieces cannot exceed 3.3 ounces.8United States Postal Service. Domestic Mail Manual – USPS Marketing Mail Flats Every Door Direct Mail-Retail

At $0.247 per piece, EDDM Retail is one of the cheapest ways to put a large-format mailer in every mailbox on a targeted route.10United States Postal Service. Every Door Direct Mail (EDDM) Campaigns commonly use 8.5-by-11 or 9-by-12 formats for these, distributing voter guides or platform overviews to entire precincts. The tradeoff is that you can’t target individual voters, so every resident on the route gets one regardless of registration status.

Space You Lose Before You Design

Size is only half the picture. USPS also dictates where addresses, barcodes, and postage go on the face of the piece, and those zones eat into your printable area. The barcode clear zone sits in the lower-right corner and measures 4.75 inches from the right edge by 0.625 inch from the bottom edge.11United States Postal Service. Domestic Mail Manual – 202 Elements on the Face of a Mailpiece No text, images, or dark colors can appear in that rectangle, because the Intelligent Mail barcode needs a clean read area for automated sorting.

The delivery address block needs its own unobstructed space so optical character readers can identify the recipient. Postage or the permit imprint goes in the upper-right corner. Between the barcode zone, address block, and postage area, a standard letter-size piece loses a meaningful chunk of one side. On a 6-by-9 mailer, roughly a third of the address side is functionally off-limits for campaign graphics.

Federal election law adds another footprint. Any mass mailing of more than 500 substantially similar pieces within 30 days must carry a “clear and conspicuous” disclaimer identifying who paid for it.12Federal Election Commission. Advertising and Disclaimers An independent expenditure with no candidate authorization needs the fullest version: the payor’s name, a permanent street address, phone number, or website, and a statement that the communication was not authorized by any candidate or candidate’s committee. The FEC requires these disclaimers to be legible and not easily overlooked, though the regulations don’t specify a minimum font size for printed mail. On a small postcard already squeezed by barcode zones and address blocks, fitting a full independent-expenditure disclaimer in readable type takes real planning.

Quick Size Reference for Political Mailers

The four categories at a glance:

  • Postcard (card rate): 3.5″–4.25″ high by 5″–6″ long by 0.007″–0.016″ thick
  • Letter: up to 6.125″ high by 11.5″ long by 0.25″ thick, with an aspect ratio between 1.3 and 2.5
  • Flat (large envelope): must exceed one letter dimension; maximum 12″ high by 15″ long by 0.75″ thick; under 16 ounces
  • EDDM Retail flat: must exceed 10.5″ long, 6.125″ high, or 0.25″ thick; maximum 15″ by 12″ by 0.75″; maximum 3.3 ounces

Every dimension counts on its own. A piece that fits the height and length limits for a letter but goes over 0.25 inch in thickness becomes a flat. A flat that fails the flexibility test becomes a parcel. The cheapest mailer is the one that sits comfortably inside its category rather than testing the edges.