Envelope sizes chart: which envelope fits your card

The right envelope is about a quarter inch larger than the card or letter inside it in each direction, so the piece slides in without bending and the envelope does not swim around it. This chart lists the common North American envelope sizes, what each one holds and what to check before you mail.

If you need envelopes printed, see our custom printed recycled envelopes. Most sizes below are available on 100% post-consumer recycled and kraft paper.

Invitation and card envelopes (A-style)

A-style envelopes are used for invitations, announcements and greeting cards. They usually have a square flap.

• A1: 3 5/8 x 5 1/8 in. Fits a 3 1/2 x 5 in card, such as an RSVP or enclosure card.
• A2: 4 3/8 x 5 3/4 in. Fits a 4 1/4 x 5 1/2 in card. The standard note card and RSVP envelope.
• A6: 4 3/4 x 6 1/2 in. Fits a 4 1/2 x 6 1/4 in card or a 4 x 6 in photo.
• A7: 5 1/4 x 7 1/4 in. Fits a 5 x 7 in card. The most common wedding invitation envelope.
• A8: 5 1/2 x 8 1/8 in. Fits a 5 1/4 x 7 7/8 in card.
• A9: 5 3/4 x 8 3/4 in. Fits a 5 1/2 x 8 1/2 in card, a half letter sheet.
• A10: 6 x 9 1/2 in. Fits a 5 3/4 x 9 1/4 in card or a tall program.

A Lee envelope is 5 1/4 x 7 1/4 in, the same size as an A7, and is often used as the outer envelope for 5 x 7 invitations.

Business envelopes (commercial)

Commercial envelopes carry letters, invoices and statements. They have a pointed or straight flap and come plain or with a window.

• #6 3/4: 3 5/8 x 6 1/2 in. Personal checks and small remittances.
• #9: 3 7/8 x 8 7/8 in. A reply envelope that fits inside a #10.
• #10: 4 1/8 x 9 1/2 in. The standard business envelope. Holds a letter size sheet folded in thirds.
• #11: 4 1/2 x 10 3/8 in.
• #12: 4 3/4 x 11 in.
• #14: 5 x 11 1/2 in. Thicker documents and legal sheets folded in thirds.

For a matched set, we print letterhead and #10 envelopes on the same recycled stock.

Catalog and booklet envelopes

Catalog envelopes open on the short side. Booklet envelopes open on the long side, which makes them easier to stuff by machine.

• 6 x 9 in: Booklets and folded brochures, and letter size sheets folded in half.
• 6 1/2 x 9 1/2 in: Holds a 6 x 9 booklet with a little room.
• 9 x 12 in: Letter size sheets, flat. Reports, proposals and certificates.
• 10 x 13 in: Pocket folders and thicker documents.

Square envelopes

Square envelopes such as 5 1/2 x 5 1/2 in and 6 1/2 x 6 1/2 in look good with square invitations and cards. In the United States they cost more to mail, because the post office cannot run square letters through its machines and adds a nonmachinable surcharge.

International (ISO) envelopes

• C6: 114 x 162 mm. Fits an A6 card or an A4 sheet folded in quarters.
• DL: 110 x 220 mm. The European business envelope, for an A4 sheet folded in thirds.
• C5: 162 x 229 mm. Fits an A5 sheet or an A4 sheet folded in half.
• C4: 229 x 324 mm. Fits an A4 sheet flat.

Mailing rules worth checking

• To mail at the letter rate in the United States, an envelope must be at least 3 1/2 x 5 in and no larger than 6 1/8 x 11 1/2 in, and no thicker than 1/4 in.
• Letters that are square, rigid, lumpy or have clasps or ribbons usually carry a nonmachinable surcharge.
• Heavy invitation suites with several cards can go over one ounce. Weigh a finished sample before you buy postage for the whole run.

Choosing a greener envelope

Ask for envelopes made from 100% post-consumer recycled paper or recycled kraft, printed with soy-based inks. Standard sizes cut more efficiently than custom ones and use less paper. Window envelopes are accepted in most curbside paper recycling programs, because the film is screened out during processing. Our guide to recycled envelopes covers papers and finishes in more detail.

Common questions

What size envelope do I need for a 5 x 7 card?

An A7 envelope, 5 1/4 x 7 1/4 in.

What size envelope fits a 4 x 6 card?

An A6 envelope, 4 3/4 x 6 1/2 in.

What size is a standard letter envelope?

A #10 envelope, 4 1/8 x 9 1/2 in, which holds a letter size sheet folded in thirds.

What envelope fits a letter size sheet without folding?

A 9 x 12 in catalog envelope.

Do square envelopes need extra postage?

Yes, in the United States square envelopes carry a nonmachinable surcharge on top of the regular letter rate.