What an envelope actually costs at the post office

Buying the envelope itself

USPS does not sell blank, unstamped envelopes at retail the way an office supply aisle does — what the Postal Store carries instead is the pre-stamped kind, postage printed on before it ever leaves the rack. Reading store.usps.com on 2026-08-31, the current #10 designs, including the U.S. Flag Forever and Northern Cardinal Forever styles in plain, window and security finishes, price at 5.30 USD for a pack of 5, about 1.06 USD per envelope. Larger case quantities are sold at the same listing at a higher total, though the site does not show the per-envelope math for those past the five-pack.

“Its postage will always be equal to the value of the stamped envelope rate in effect at the time of use.” — USPS, Postal Store product listing for a Forever-value stamped envelope, read 2026-08-31.

That line is the whole point of buying one pre-stamped: the envelope keeps its postage value even after a rate increase, exactly the way a loose Forever stamp does. Handling on a Postal Store order adds 2.10 USD on orders up to 50 USD and 2.85 USD above that, per checkout on 2026-08-31, so an order bought online is not quite the shelf price.

Which price list an envelope actually falls into

USPS physical standards, read pe.usps.com on 2026-08-31, set the dimensions each class has to sit inside. Weight decides the price within a class; these limits decide which class an envelope is in to begin with.

• A #10 business envelope is 4-1/8 x 9-1/2 in, inside the letter box on every dimension, so it prices off the letter table above.
• A small note card, sent loose without an envelope, can qualify as a postcard if it sits at or under 6 x 4-1/4 in. Put it in an envelope, even a small one, and it is a letter instead — the envelope itself pushes it out of postcard rules.
• A 6x9-and-up envelope sits at the boundary between letter and large envelope. USPS physical standards also require a machinable letter to hold a length-to-height ratio between 1.3 and 2.5, and to be flat and rectangular; a padded, clasped or stuffed 6x9 usually fails that test and is priced as a large envelope even though its printed dimensions would fit a letter.
• Clasps, strings or buttons are named directly among USPS's nonmachinable characteristics for letters, which is what triggers the 0.49 USD surcharge above even on an envelope that otherwise qualifies for letter rates.

Where these rules come from

• USPS, Notice 123 price list — postcard, letter and large envelope prices, and the nonmachinable surcharge. Effective July 12, 2026, read 2026-08-31.
• USPS, DMM 101, Physical Standards for Mailpieces — postcard, letter and large envelope dimensional limits, the letter aspect-ratio rule and the nonmachinable characteristics list. Read 2026-08-31.
• USPS, Postal Store, Stamped Envelopes — pre-stamped envelope pricing and the Forever-value postage statement. Read 2026-08-31.

USPS revises postage rates and Postal Store prices without much notice. Treat the figures above as what those pages stated on 2026-08-31 and check usps.com before buying in bulk.