Postcard postage is one of the few places where a small design decision has a direct, multiplied cost. Get the dimensions wrong and every piece in the run costs more.
The three tiers
USPS prices mail by category, and the category is determined by physical dimensions.
Postcard rate
The cheapest option, reserved for cards within a specific size window. To qualify, a card must be rectangular, at least 3.5 x 5 inches, no larger than 4.25 x 6 inches, and between 0.007 and 0.016 inches thick.
This is why the classic 4 x 6 postcard is so common. It sits comfortably inside the window.
Letter rate
Exceed the postcard maximum and the piece is priced as a letter, which costs more. Letter-size mail runs up to 6.125 x 11.5 inches and up to 0.25 inches thick. A 5 x 7 or 6 x 9 card falls here.
Flat rate
Larger than letter dimensions and the piece becomes a flat, at a higher rate again. This is also the category EDDM pieces must fall into, which is why EDDM has a minimum size rather than a maximum.
The trap
A 4.25 x 6 inch card qualifies for postcard rate. A 4.5 x 6 inch card does not. That quarter inch moves the whole mailing into letter pricing. On a run of 5,000 pieces the difference is substantial and entirely avoidable.
Decide your postage tier before you design, not after. Ask us or check current USPS pricing first, then build the artwork to fit the tier you have chosen. Redesigning a finished postcard to shave a quarter inch is a miserable job.
Thickness matters too
Postcard rate requires the piece to be at least 0.007 inches thick and no more than 0.016 inches. Order too light and it is not machinable; order a heavy 16pt card and you may exceed the postcard thickness limit even though the dimensions qualify. Standard 14pt sits in range.
Design requirements
- Leave the address area clear. USPS requires defined clear space for the address block and barcode, typically the bottom right of the address side.
- Do not print heavy dark ink where the barcode goes. It interferes with automated reading.
- Keep the indicia area clear if you are mailing with a permit or EDDM.
- Aim for high contrast in the address area so automated equipment reads it reliably.
When bigger is worth it
Sometimes paying the higher rate is the right call. A 6 x 9 card at letter rate stands out in a stack of standard mail in a way a 4 x 6 does not. If your response rate improves by more than the postage difference, the larger card wins.
And for EDDM specifically, the calculation inverts entirely: postage is the same per piece regardless of size within the qualifying range, so you should generally go as large as your printing budget allows.
Verify before you print
USPS pricing and rules change. Confirm current dimensions and rates before committing to a large run, or ask us and we will check against the current standards as part of quoting the job.
See postcard options on our marketing materials page.
Need this printed? We are on Hillside Avenue in Jamaica, Queens.