The short answer
To send a postcard in the US, write your message on the left half of the address side, write the recipient’s address on the right, and put a $0.65 postcard stamp in the upper-right corner. Then put it in your home mailbox with the flag up, drop it in a blue collection box, or hand it in at a Post Office. That price covers cards up to 4-1/4 × 6 inches; larger cards need letter postage, and a card to another country needs a $1.75 Global Forever stamp.
How do you send a postcard, step by step?
Sending a postcard takes five minutes and one stamp. The order matters less than getting each piece right, but this sequence avoids wasted stamps:
1. Check the size. A rectangular card no bigger than 4-1/4 × 6 inches mails at the postcard price. Anything larger costs letter postage.
2. Write your message on the left half of the address side, leaving the right half and the bottom strip clear.
3. Address it: the recipient’s name, street address, and city, state, and ZIP Code on the right half, plus your return address in the upper-left corner if it fits.
4. Add postage last: a $0.65 postcard stamp in the upper-right corner for a standard card in the US.
5. Mail it from your home mailbox with the flag raised, an outgoing slot in a cluster mailbox, a blue collection box, or a Post Office.
The sections below explain each step and the questions that usually come up along the way: envelopes, missing stamps, international cards, and tracking.
Does my postcard qualify for the postcard price?
The cheaper postcard price only applies to cards in a specific size range. Under DMM 201.1.2, a card must be rectangular and at least 3-1/2 inches high, 5 inches long, and 0.007 inch thick, and no more than 4-1/4 inches high, 6 inches long, and 0.016 inch thick. A typical 4 × 6 souvenir card fits. So does a 5.5 × 4.25 card.
Larger cards like 5 × 7 or 6 × 9 are still mailable, but USPS prices them as letters. A card thinner than 0.007 inch is too flimsy to mail. Square cards cost more because they’re treated as nonmachinable; USPS says square or vertical pieces need extra postage.
If you’re not sure what size you have, measure it. A ruler settles it faster than guessing.
How do you write and address a postcard before mailing it?
The address side does all the work. The left half is for your message; the right half is for the recipient’s address; the upper-right corner is for the stamp; and the bottom strip on the right should stay blank so USPS can print a barcode there (DMM 202.5.1 reserves a clear zone 4-3/4 inches wide and 5/8 inch high).
USPS asks you to print addresses neatly in capital letters with a pen or permanent marker, skip commas and periods, and include the ZIP+4 Code when you can. A return address is optional on a postcard, but if you add one it goes in the upper-left corner (DMM 602.1.5). Without one, USPS can’t send the card back to you if something is wrong with it.
Keep in mind that a postcard isn’t private. Anyone who handles it can read it, so leave off account numbers, health details, and anything that tells strangers your house is empty. For message ideas and a full addressing example, see the two guides linked below.
Do postcards need a stamp, and which one?
Yes. Every postcard you drop in the mail needs postage. For a standard-size card going anywhere in the US, that’s a $0.65 postcard stamp (USPS Notice 123). DMM 604.1.7 says stamps must be affixed in the upper-right corner of the address side; most printed postcards have a small box there.
A Forever stamp works too. It’s worth $0.82, the 1-ounce letter price, so you’ll overpay by 17 cents, and USPS doesn’t give change. That’s often fine if it’s the only stamp in your drawer. Oversized postcards (anything over 4-1/4 × 6 inches) actually need letter postage, so a Forever stamp is the right stamp for those. You can also combine smaller stamps that add up to the required amount.
Cost questions have their own guide: see how much a postcard stamp is for current prices, what changed in July 2026, and where to buy postcard stamps.
Can you mail a postcard without a stamp or with too little postage?
No. Under DMM 604.8, mail that reaches the Post Office with no postage at all is endorsed “Returned for Postage” and sent back to the sender without an attempt at delivery. If there’s no usable return address, it can’t come back to you.
A card with some postage, but not enough, is handled differently. DMM 604.8 says a shortpaid piece is marked with the amount owed and delivered to the addressee once they pay it. If they refuse, a First-Class piece with a return address comes back to you marked “Returned for Additional Postage.” Shortpaid nonmachinable First-Class Mail letters go straight back to the sender.
The most common way to end up short is an oversized card with a postcard stamp on it. A 5 × 7 card with a $0.65 stamp is $0.17 short of the $0.82 letter price, and your friend may be the one asked to pay the difference. Measure first, then stamp.
Where do you mail a postcard?
Once the card is addressed and stamped, USPS lists four ways to send it:
- Put it inside your home mailbox and raise the flag, if your mailbox has one. Your carrier picks it up on the normal route.
- If you have a cluster mailbox, drop it in the outgoing mail slot.
- Drop it in a blue collection box. USPS’s locator shows box locations and last pickup times.
- Take it to a Post Office lobby drop, or hand it to a retail associate at the counter.
Do postcards need an envelope?
No. USPS describes postcards as being for short messages you don’t need to put in an envelope. The card itself is the mailpiece: address, stamp, and message all go on its back.
You can put a postcard in an envelope if you want the message to stay private or the picture to stay clean, but then it’s a letter. Address the envelope, not the card, and pay letter postage: a $0.82 Forever stamp for a standard envelope up to 1 ounce. The postcard stamp price no longer applies.
Quick reference: postage and where to mail it
Prices are USPS retail prices from Notice 123. Weight isn’t a factor for a single card; size and destination are.
| Situation | Postage | Where to mail |
|---|---|---|
| Standard card (up to 4-1/4 × 6 in) to a US address | $0.65 postcard stamp | Home mailbox with flag up, cluster box slot, blue collection box, or Post Office |
| Standard card, but you only have a Forever stamp | $0.82 Forever stamp (overpays by $0.17) | Any of the above |
| Oversized card (5 × 7, 6 × 9) to a US address | Letter postage: $0.82 Forever stamp | Any of the above |
| Square card | Extra postage for nonmachinable pieces; check at a Post Office | Post Office counter, so it’s weighed and priced |
| Postcard sealed in an envelope | Letter postage: $0.82 Forever stamp | Any of the above |
| Any card to another country | $1.75 Global Forever stamp | Any of the above; write the country in English on the last line |
| No stamp at all | Not mailable; returned to sender for postage | Don’t mail it yet |
How do you send a postcard internationally?
USPS says it costs $1.75 to send a postcard to any other country with a Global Forever stamp. Put the stamp in the space provided near the delivery address, the same corner you’d use at home. Larger or square postcards cost more.
For the address, USPS asks you to write the delivery address in English (you can add the local-language version as long as the English translation follows each line), and put the destination country’s name in English on the last line. Many countries put the postal code before the city; follow the format of the country you’re mailing to. USPS also says First-Class Mail International pieces need “AIRMAIL/PAR AVION” on the address side.
A postcard is correspondence, so you don’t need a customs form. You mail it the same ways as a domestic card: your mailbox, a blue box, or a Post Office. Mail to APO/FPO/DPO addresses and US territories uses domestic postage, not a Global Forever stamp.
How long does it take a postcard to arrive, and can you track it?
Postcards travel as First-Class Mail, which USPS estimates at 1–5 business days within the US. That clock starts when the card enters the mailstream, so a card dropped in a collection box after the last pickup time won’t move until the next pickup.
A stamped postcard doesn’t come with a tracking number. USPS describes First-Class Mail as trackable only “with certain extra services,” and a stamp alone doesn’t buy any of them. For international mail, USPS says plainly that you can’t get tracking on First-Class Mail International letters. If you need proof that something arrived, a stamped postcard is the wrong format.
Can you send a postcard online?
Yes. Several online services print a postcard from your photo or design and mail it for you, so you never buy a stamp or find a mailbox. Compare what each includes: card size, whether postage is in the price, and which countries they deliver to.
With IRIS, you pick one of our illustrated designs or upload your own photo (JPEG, PNG, or WebP), edit the front greeting, type the message for the back, and enter the sender and recipient addresses. You preview both sides, then pay through Stripe Checkout; no account is needed. A 4 × 6 postcard is $3.49 and a 6 × 9 postcard is $4.49, including full-color printing and USPS First-Class Mail postage. The address block, postage, and barcode area on the back are laid out for you, and a private order link shows production status and any USPS events reported.
Know the limits before you start. IRIS mails only to US addresses, so it can’t send an international postcard. Your message is printed, not handwritten. And there’s no scheduled send date: the card goes into production after you pay, so order a few days ahead of a birthday rather than counting on a specific arrival day.
Sources & further reading
Product details checked against the IRIS API contract when this article was published. Platform references can change; consult the linked documentation when implementing.
- USPS: How to send a letter or postcard (domestic)
- USPS: How to send a letter or postcard internationally
- USPS: First-Class Mail
- USPS DMM 201: Physical standards
- USPS DMM 202: Elements on the face of a mailpiece
- USPS DMM 602: Addressing
- USPS DMM 604: Postage payment methods
- USPS Notice 123: Price list
Published by IRIS Postal Forms, operated by Great Lakes Computing Office LLC. Send a correction.