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Yes. USPS accepts homemade postcards as long as they fit the size window (3.5 by 5 inches minimum, 4.25 by 6 inches maximum), use card stock thick enough to survive the sorting machines, and keep the address area clear. Stick to roughly standard postcard proportions, longer than tall, and skip heavy gloss that can smear in processing.
The window is strict: no smaller than 3.5 by 5 inches, no larger than 4.25 by 6 inches for the postcard rate. Go bigger and it mails as a letter instead, which costs more and needs an envelope-friendly shape. There is also a proportion rule most people have never heard of: the card's length divided by its height has to fall within the range USPS publishes (roughly, at least a third longer than tall and no more than about two and a half times as long). A square card fails this test and gets surcharged or returned.
| Requirement | What to do |
|---|---|
| Size | Between 3.5 x 5 in and 4.25 x 6 in |
| Shape | Rectangular, longer than tall, within the published proportion range |
| Paper | Card stock, not printer paper; it must survive high-speed sorters |
| Address side | Keep the right half and bottom edge clear for the address and barcode |
| Finish | Matte or light satin; heavy gloss can smear the postmark |
Regular printer paper is too flimsy: it jams or tears in the sorting equipment, and a torn postcard does not get delivered out of sympathy. Use proper card stock, the kind sold as blank postcards or heavyweight cover stock. If you are printing at home, check your printer's paper-weight limit first; many home printers cap out below ideal postcard stock, in which case a local print shop can run them on the right paper for a small batch.
Finish matters more than people expect. A heavy gloss coating looks great but the postmark ink can smear across it, and some coatings confuse the optical readers that sort the mail. Matte or a light satin finish is the safe choice. If your design is dark, keep the address area on a light panel: machines read contrast, and white text on a black background is a gamble.
Follow the standard layout: stamp in the top right corner, delivery address in the lower right area, your message on the left. Leave the bottom edge of the address side clear, because USPS prints its routing barcode there; text or artwork in that strip can get covered or cause a misread. Canada Post has its own postcard size rules, so if you are mailing to Canada, check their dimensions before you print: a card that is fine for USPS is usually fine for Canada Post too, but the postage and size bands are separate systems.
One last tip: test one before you print fifty. Mail a single card to yourself and see how it arrives. If the barcode printed cleanly and nothing smeared, your batch is good to go.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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