Envelope Sizes Explained: #10, A-Sizes and Catalog Envelopes

The #10 envelope, at 4 1/8 x 9 1/2 inches, is the standard business envelope in North America: a letter-size sheet folded in thirds slides into it exactly. Around it sit two other families, A-size (announcement) envelopes for cards and invitations, and catalog envelopes like 9 x 12 for documents mailed flat.

Numbered commercial envelopes (#9, #10) are for correspondence; the #9 nests inside a #10 as a reply envelope. A-sizes (A2, A6, A7) match common card formats, an A7 carries a 5 x 7 card. Catalog sizes carry unfolded pages.

Window or windowless

A window envelope shows the address printed on the document inside, so there is nothing to address by hand or label, the standard for invoices and statements where the address position is fixed by the letterhead layout. A windowless #10 is the choice for correspondence, cheques accompanied by letters, and anything where the contents should stay private at a glance.

Printing on envelopes

A printed envelope carries your return address, logo and brand colour, so the piece is identified before it is opened. We print full-colour #10 envelopes, with or without a window, matched to the letterheads they carry; artwork needs the same care as any print file, keep critical elements clear of the flap and window zones.

Which one for your job?

Choose the #10 for business mail, with a window if your documents place the address to show through it, without for general correspondence; the #10 is the size you can order directly in our online store. Documents that must arrive unfolded, contracts, certificates, photographs, call for a catalog envelope instead, and invitations for an A-size; we print those formats as custom orders, so ask and we will quote yours. Unsure whether your layout suits the window position? Send the document and we will check it against the envelope before printing.

Common questions

What fits in a #10 envelope?

A letter-size (8 1/2 x 11) sheet folded in thirds, which is why it is the default for invoices, letters and statements. Several sheets fit, though past a few the envelope thickens beyond standard postage.

Which envelope sizes do you print?

The #10 business envelope, window and windowless, prints in full colour and is available directly in our online store. Other formats, A-size invitation envelopes, 6 x 9 and 9 x 12 catalog envelopes, custom dimensions, we print as custom orders: contact the shop and we will quote yours.

Where does the window sit on a #10 window envelope?

In the standard position on the lower left of the front, sized so an address block placed correctly on a letter-size document shows through after a tri-fold. We can check your document layout against it before you print a run.

Products where this term matters

See also in the dictionary: Paper weight and finishes, Bleed · full dictionary