Postage for a 6×8 card runs at least $1.27 domestically, and often $1.63 or more, because the card almost never qualifies for the standard letter rate on its own. The exact amount depends on whether the envelope stays within letter dimensions and whether the card is stiff enough to trip the non-machinable surcharge. A single Forever stamp is not enough.
Measure the Envelope, Not the Card
The card itself is 6 by 8 inches, which fits inside the USPS letter maximum of 6-1/8 inches high by 11-1/2 inches long by 1/4 inch thick.1Postal Explorer. Sizes for Letters But you’re not mailing a bare card. You’re mailing it in an envelope that has to be slightly larger to hold it, and that’s where classification gets decided.
If the envelope’s height goes over 6-1/8 inches by even a fraction, the whole piece jumps from a letter at $0.78 per ounce to a flat at $1.63 per ounce.2Postal Explorer. Notice 123 – January 2026 Price Change Some envelopes made for 6×8 cards hold the height at exactly 6 inches and squeak under the limit. Others run a quarter-inch taller and cost you nearly double. Pull out a ruler before you buy stamps.
A flat can go up to 12 inches high by 15 inches long by 3/4 inch thick.3Postal Explorer. Sizes for Large Envelopes and Flats So a taller envelope is still mailable, just at the higher rate.
The Non-Machinable Surcharge on Greeting Cards
Even when a 6×8 card in its envelope fits letter dimensions, it will almost certainly owe an extra $0.49 non-machinable surcharge on top of the letter rate.2Postal Explorer. Notice 123 – January 2026 Price Change The fee applies to mail that can’t run through automated sorting equipment and has to be handled by a person.
A letter-size piece is non-machinable if any of the following is true:4USPS. DMM 101 Physical Standards for Retail Letters, Flats, and Parcels
- It’s too rigid to bend easily under 40 pounds of belt tension around an 11-inch turn. Cardstock, glued layers, and embellishments almost always fail this test.
- It has uneven thickness from ribbon, buttons, coins, or anything else inside the envelope.
- It has closure devices on the envelope itself, such as clasps, strings, or buttons.
- Its length divided by its height falls outside the 1.3 to 2.5 range. A 6×8 envelope works out to about 1.33 and just clears the minimum.
Rigidity is the usual reason greeting cards come up short. If you’ve ever received a card with a postage-due notice, that was probably why.
What You’ll Actually Pay
All of these prices assume the card weighs one ounce or less:
- A thin, flexible card in a letter-size envelope: $0.78. Uncommon for greeting cards, but possible for a single-sheet card in a plain envelope that stays under 6-1/8 inches tall and bends easily.
- A typical greeting card in a letter-size envelope: $1.27, which is the $0.78 letter rate plus the $0.49 non-machinable surcharge.2Postal Explorer. Notice 123 – January 2026 Price Change
- A card in an envelope taller than 6-1/8 inches: $1.63 at the flat rate. The non-machinable surcharge doesn’t apply on top of this, since the higher rate already covers manual handling.3Postal Explorer. Sizes for Large Envelopes and Flats
- A card over one ounce: add $0.29 per additional ounce as a letter, or $0.27 per additional ounce as a flat. Photos, gift cards, and thick inserts push cards past one ounce easily.
Two Forever stamps ($1.56) cover the non-machinable letter scenario with a little room to spare. For a flat, two Forever stamps come up seven cents short of $1.63, so you’d need to add a small additional-postage stamp or buy exact postage at the counter or online.
What Happens If You Underpay
If you shortpay, the carrier delivers the card with a postage-due notice, and the recipient has to pay the difference in cash before they can have it.5USPS. How is Undeliverable and Misdelivered Mail Handled If the recipient refuses or isn’t around, the piece goes back to the return address stamped “Returned for Additional Postage.” Mail sent with no postage at all goes straight back to the sender.
Holiday greeting cards get a small break. During December, the USPS makes a special effort to deliver postage-due greeting cards rather than send them back.5USPS. How is Undeliverable and Misdelivered Mail Handled
Mailing a 6×8 Card Internationally
International postage follows a separate schedule. A Global Forever stamp costs $1.70 and covers a one-ounce First-Class Mail International letter.6USPS. 2026 Postage Price Change The size limits are the same as domestic letters: 11-1/2 inches long by 6-1/8 inches high by 1/4 inch thick.7USPS. How to Send a Letter or Postcard International
An envelope larger than those dimensions becomes an international large envelope, and pricing varies by destination country and weight.7USPS. How to Send a Letter or Postcard International The $0.49 non-machinable surcharge also applies to international letters.2Postal Explorer. Notice 123 – January 2026 Price Change For international mail, take the card to the counter.
How to Confirm Before You Mail
Two tools answer nearly every classification question: a ruler and a scale. Measure the envelope’s height first. If it’s over 6-1/8 inches, you’re paying $1.63 or more and can stop there. If it’s under, check the flex. Hold the sealed envelope by one short edge and let it hang. A card that droops and bends might qualify as a standard machinable letter. A card that holds its shape like a board owes the $0.49 surcharge.
When you’re not sure, take it to a post office counter. Clerks have thickness gauges and dimension templates, and they’ll weigh, classify, and print exact postage on the spot. The USPS online postage calculator can give you an estimate first if you’d rather not guess.