Postcard size: standard dimensions and USPS rules

Standard postcard size: start with retail rules

The size of a regular postcard and the size eligible for a particular postage price are separate questions. USPS Business Mail 101: cards gives the retail dimensions summarized above. A printer's label such as standard, oversized or jumbo does not determine the postal category.

USPS DMM 101, section 6.2 also requires rectangular, uniformly thick, unfolded cards. A suitable outline alone does not establish eligibility; the material and construction matter too.

• Trim size

  The dimensions of the physical card after cutting. Put these dimensions on the purchase order and measure the proof against them.

• Finished thickness

  Ask for measured caliper, including coatings or bonded layers. A stock name or paper weight is not a substitute for the finished measurement.

• Address orientation

  For letter-size mail, length runs parallel to the delivery address as read. Mark that direction on the proof so the designer and mailer assess the same layout.

Postcard size chart: 4 × 6 through 6 × 11

Use this chart to shortlist formats, then confirm the full specification with the mailer. The centimeter values are calculated using the NIST inch conversion, 1 inch = 2.54 centimeters. Sizes are height × length with the address parallel to the longer edge.

Postcard size photo prints versus mailpieces

A photo print with the right outline is not automatically a mailable card. Confirm its stock, back surface, thickness and ability to take legible addressing before ordering photo postcard prints. For production choices beyond dimensions, use the postcard printing guide.

Ask suppliers to compare the same finished dimensions, quantity and mailing method. A print-only quote for a large card cannot be compared directly with a prepared, addressed and mailed smaller card.

Large postcard size: letter or flat?

A 6 × 11.5 inch card fits within the letter-size dimensional ceiling. The actual USPS maximum is 6.125 inches high × 11.5 inches long × 0.25 inch thick, according to USPS Business Mail 101: letters. Weight, shape and other requirements still apply.

Ordinary flat dimensions exceed at least one letter maximum and stay within 12 inches high × 15 inches long × 0.75 inch thick. See USPS Business Mail 101: flats; EDDM has an exception discussed below. A flat must also meet flexibility and uniformity standards, or package treatment can apply, as USPS First-Class Mail guidance explains.

Jumbo postcard size is a sales description, so request exact dimensions. For the broader format decision, compare direct mail postcards.

USPS postcard size, aspect ratio and surcharges

For machinable letters and commercial cards, length divided by height generally must fall from 1.3 to 2.5, inclusive. The USPS Quick Service Guide 201 explains aspect ratio and common nonmachinable characteristics. An eligible rectangle can still fail another processing requirement.

Formula: length parallel to address ÷ height perpendicular to address.
4 × 6 card: 6 ÷ 4 = 1.5, inside the range.
6 × 9 card: 9 ÷ 6 = 1.5, inside the range.
5 × 5 square: 5 ÷ 5 = 1, outside the range.
Passing this calculation is not complete postal approval.

Show the reviewer a finished sample with the real finish and attachments. Keep the written category decision with the approved artwork, especially if a supplier proposes changing stock after approval.

Postcard sizes for EDDM: a different flat rule

EDDM-Retail uses USPS Marketing Mail flats, rather than the retail First-Class postcard category. USPS Quick Service Guide 140 sets minimum dimensions of 3.5 inches high × 5 inches long × 0.007 inch thick, plus the size test below.

• 6 × 9: insufficient outline

  At ordinary postcard thickness, it exceeds none of the EDDM thresholds. Its suitability for a targeted First-Class campaign does not make it suitable for EDDM.

• 6 × 11: length candidate

  Its length passes the EDDM size test even though the outline also fits letter dimensions. The mailing must still meet the EDDM requirements.

• 6.5 × 9: height candidate

  Its height passes the test. Confirm the remaining physical characteristics, postal markings and preparation with the provider.

Choose EDDM when route coverage matches your audience; choose a researched address list when individual businesses matter. Our Every Door Direct Mail guide covers that decision. Fer Marketing's personalized postcard offer includes First-Class mailing, so do not treat its price as an EDDM quote.

Postcard size template: trim, bleed and clear zones

Start with the printer and mailer's template for the selected format. A blank rectangle downloaded from a design tool may describe trim without accounting for address printing, postage or postal processing. Use the direct mail design guide for the creative brief.

Adobe's print bleed guide explains artwork extending beyond the finished cut. Get bleed and safe-margin values from your own printer; neither is a universal USPS postcard-size requirement. Postal eligibility is assessed on the trimmed mailpiece.

How to choose the best postcard size for direct mail

The best postcard size for direct mail is the smallest format that makes the message readable, fits the chosen service and meets your budget. Size alone does not predict response. Use this process before comparing suppliers or committing to a print run.

1. Step 1

   Define the recipient and message

   Write the audience, reason for contacting them and requested next action. Decide whether the job needs a named business list, route coverage or a handout before choosing a postal product.

2. Step 2

   Shortlist finished formats

   Place the actual headline, visual and explanation into candidate layouts. Print mockups at physical size and remove content that does not help the recipient understand the message.

3. Step 3

   Confirm the mailing category

   Send dimensions, address direction and proposed construction to the mailer. Ask whether its quote uses retail First-Class, qualifying commercial First-Class, Marketing Mail letters or EDDM flats, and who verifies eligibility.

4. Step 4

   Price the complete job

   Compare research or list work, artwork, variable data, printing, preparation and postage. Keep scope and quantity consistent across options, and ask how a rejected format or stock substitution would change the quote.

5. Step 5

   Approve the production proof

   Check caliper, legibility, trim, clear zones, addresses and the printed QR destination. Resolve postal questions with the mailer or a USPS Mailpiece Design Analyst before releasing files.

6. Step 6

   Record the approved specification

   Save the final artwork, sample, supplier approval and mailing category. Name the person who can authorize changes, and require another review if finished dimensions, construction or address orientation change.

A print postcard size brief you can send

Send the same written brief to every supplier. A clear brief exposes missing work and lets you decide whether printing alone, printing with mailing, or a personalized campaign solves the actual problem.

Audience and distribution: [named recipients / routes / handouts].
Quantity and finished size: [count], [height × length in inches].
Postal service and price category: [supplier to confirm in writing].
Stock and finish: [proposed product], measured finished caliper required.
Artwork: supply trim, bleed, safe area and postal-zone template.
Variable content: [names, findings, images, QR destinations].
Proof: [digital and/or physical], reviewer [name], approval [method].
Itemize design, data, printing, preparation, postage and shipping.
Confirm exclusions, substitutions, reprint responsibility and handoff date.

For a job you arrange yourself, check the current USPS price list after confirming the category. Do not estimate postage from the printer's product name. Compare the complete scope using our postcard marketing cost guide.

Where Fer Marketing's postcard service fits

Fer Marketing provides researched, personalized postcards for agencies and businesses targeting other businesses. We are operated by Fer LLC in Wyoming, founded by Fernando Marcano, an IT engineer with 20+ years of hands-on experience. We serve the US market in English and Spanish.

• Research through mailing

  Prospect research, one verified finding about each prospect's website, design, printing and USPS First-Class postage are included. Each card has a QR code to a branded report page about that prospect.

• Published campaign prices

  $10 per custom postcard with a 50-card minimum ($500). The intro pack for a first campaign includes 100 custom postcards for $500 ($5 per card).

• White-label for agencies

  Agencies can run the campaign under their own brand. Confirm the format and campaign scope in the written quote before paying by card through Stripe.

Review the personalized postcard service, or contact us with your audience and message. We reply the same business day, 9 AM to 9 PM ET, through WhatsApp or fer@fer.marketing, and confirm scope and price before work.