Postcard Size: Standard Dimensions & USPS Mailing Rules
The standard postcard size is 4 × 6 inches. Learn USPS postcard dimensions, mailing rules, common postcard sizes, and postage requirements.
This guide explains standard postcard dimensions, USPS mailing limits, popular postcard formats, and how postcard size affects postage costs.
📮 Standard Postcard Size
The standard postcard size is 4 × 6 inches. It qualifies for USPS postcard postage and easily passes through automated mail sorting equipment.
📏 USPS Postcard Size Rules
| Rule | Measurement |
|---|---|
| Minimum Size | 3.5 × 5 inches |
| Maximum Size | 4.25 × 6 inches |
| Thickness | 0.007–0.016 inches |
📐 Common Postcard Sizes
4 × 6
Standard USPS postcard size with the lowest mailing cost.
5 × 7
Popular for invitations, greeting cards, and artwork.
6 × 9
Marketing postcards that stand out in the mailbox.
Rack Card
3.5 × 8.5 inches for travel displays and brochures.
🌍 Postcard Size vs A5 & A6
A6 (105 × 148mm) is the closest ISO paper size to a standard postcard, while A5 (148 × 210mm) is much larger and closer to a 5×7 postcard.
💌 Postage by Postcard Size
| Postcard Size | Postage |
|---|---|
| 4 × 6 | USPS Postcard Rate |
| 5 × 7 | First-Class Letter Rate |
| 6 × 9 | Letter or Flat Mail Rate |
| 8.5 × 11 | Flat Mail / Letter |
🎨 Common Design Mistakes
Skip Bleed
Always include bleed to prevent unwanted white edges after trimming.
Safe Margins
Keep important text away from postcard edges to avoid trimming.
Wrong Size
Exceeding USPS limits increases mailing costs.
❓ Frequently Asked Questions
Are postcards typically 4×6 or 5×7?
4×6 is the standard USPS postcard size. 5×7 is common but mails at the letter rate.
Can I mail a 5×7 card as a postcard?
No. A 5×7 card exceeds USPS postcard size limits and requires First-Class letter postage.
Is a postcard A5 or A6?
Neither exactly. A6 is closest to a standard postcard, while A5 is considerably larger.
Can you mail an 8.5×11 postcard?
Yes, but it is mailed as a letter or flat, not as a USPS postcard.
What are USPS rules for postcards?
Cards must measure between 3.5×5 and 4.25×6 inches with a thickness between 0.007 and 0.016 inches.
How much postage do I need for a 5×7 postcard?
A First-Class Mail letter stamp is required.
Does a 6×9 postcard require extra postage?
Yes. It exceeds USPS postcard dimensions and is mailed at the letter or flat rate.
Do postcards just need one stamp?
Only standard-size postcards qualify for USPS postcard postage. Larger postcards require letter postage.
What are common postcard design mistakes?
The most common mistakes are skipping bleed, placing text too close to the edge, and exceeding USPS size limits.
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