Direct Mail Postcard Sizes: USPS Requirements & Best Practices
Choosing the right postcard size affects postage cost, mailbox visibility, and response rates. This guide covers all standard USPS postcard sizes, postage rates for each, and recommendations for different campaign types.
USPS Postcard Size Categories
- Standard postcards (letter-size): Minimum 3.5" × 5", maximum 4.25" × 6". Qualifies for First-Class postcard rate ($0.56 retail, $0.48 metered, lower with presort).
- Large postcards (letter-size): 4.25" × 6" to 6.125" × 11.5". Qualifies for First-Class letter rate or Marketing Mail letter rate.
- Flat-size postcards: Minimum 6.125" × 11.5", maximum 12" × 15". Required for EDDM. Qualifies for Marketing Mail flat rate or EDDM Retail ($0.247/piece).
Common Postcard Sizes
- 4" × 6": Most affordable to mail. Good for appointment reminders, thank-you cards, and simple announcements.
- 5" × 7": More design space. Good for event invitations and product announcements.
- 6" × 9": Oversized — stands out in the mailbox. Good for retail promotions and real estate.
- 6" × 11": Maximum letter-size. High visibility with room for detailed messaging.
- 6.25" × 11.5" (EDDM minimum): Required minimum for EDDM campaigns. Lowest per-piece postage for saturation mailings.
- 8.5" × 11": Full-page flat. Maximum design space for menus, maps, and detailed promotions.
- 9" × 12": Large flat. Premium format for high-impact campaigns.
Size Selection Guide
- Budget priority: 4×6 standard postcard (lowest postage)
- Visibility priority: 6×9 or 6×11 oversized (stands out in mailbox)
- EDDM campaigns: 6.25×11.5 minimum (required for EDDM pricing)
- Maximum impact: 8.5×11 or 9×12 flat (most design space)
Design Requirements
- Address panel: minimum 4" wide × 2" tall on the right half of the back
- Barcode clear zone: 4.5" × 0.625" at bottom of address side
- Return address: upper left corner of address side
- Postage area: upper right corner of address side