How Postcard Size and Shape Affect Mailing Eligibility

Postcard size and shape can affect how your piece is mailed, what postage category it falls into, and whether it qualifies for standard postcard rates. A postcard may look great, but if the size, shape, or mailing layout does not meet postal requirements, it may need extra postage or special handling.

Use this guide before choosing a custom postcard size or shape for a mailed campaign.

Quick Answer

Standard postcards are usually easiest to mail when they are rectangular, correctly sized, and thick enough for postal processing.

Custom sizes and shapes can still be mailed in many cases, but they may not qualify for standard postcard rates. Square, oversized, folded, die-cut, or unusually shaped postcards may be treated as letters, flats, or non-machinable mail depending on the final piece.

If postage cost matters, confirm mailing eligibility before printing.

Size and Shape Basics

Postcard size affects how the piece moves through postal equipment and how it is priced. Smaller postcards may qualify for standard postcard mailing rates if they meet USPS size and thickness requirements. Larger postcards offer more design space but may fall into a different mail category.

Common postcard sizes include:

• 4" × 6"

• 5" × 7"

• 5.5" × 8.5"

• 6" × 9"

• 6" × 11"

Shape also matters. Rectangular postcards are usually the safest option for mailing because they are easier for postal equipment to process.

Shapes that may require extra review include:

• Square postcards

• Circle or oval postcards

• Half-circle postcards

• Leaf-shaped postcards

• Custom die-cut postcards

• Folded postcards

• Irregular or asymmetrical shapes

These formats can create stronger visual impact, but they may require different postage or special handling.

Custom-Shaped and Die-Cut Postcards

Die-cut postcards are useful for promotions, invitations, announcements, and event mailers that need to feel more distinctive. However, custom shapes may not qualify for the same mailing rates as standard rectangular postcards.

Before ordering a custom-shaped postcard for mailing, check:

• Final size

• Shape

• Thickness

• Edge design

• Mailing side layout

• Address and postage placement

If the postcard is mainly for handouts, packaging inserts, or event distribution, mailing eligibility may be less important. If it will be mailed, confirm the requirements first.

Mailing Side Layout

The mailing side needs enough clear space for postal processing.

Leave room for:

• Recipient address

• Return address, if used

• Postage, stamp, or mailing indicia

• Barcode or postal marking area

• Required clear zones

Avoid placing important artwork, QR codes, coupons, or key messages in the address or postal marking area. A clean mailing layout helps reduce the risk of delays, scanning issues, or returned mail.

Design Tips for Mailed Postcards

For better results:

• Choose a mail-friendly size when postage cost matters

• Keep important details away from trim edges

• Leave clear space for the address and postage

• Use high contrast for contact information

• Keep QR codes away from postal markings

• Confirm requirements before using custom shapes

• Review all dates, phone numbers, URLs, and offer details before ordering

The more unusual the postcard shape, the more important it is to check mailing requirements early.

Before You Order

Before printing postcards for mailing, check:

• Is the postcard size suitable for your mailing plan?

• Is the shape compatible with your postage goal?

• Does the piece need to be rectangular to qualify for a lower rate?

• Is the cardstock thick enough for mailing?

• Is there enough space for the address, postage, and postal markings?

• Have you confirmed the final requirements with USPS or your mailing service?

If you are using a custom shape, confirm mailing eligibility before production. This helps avoid postage surprises, processing issues, or campaign delays.