Envelope size chart
| Envelope | Size (inches) | What fits |
|---|---|---|
| #6 3/4 | 3 5/8 x 6 1/2 | Remittance slips, checks, small reply mail, letter folded in quarters |
| #9 | 3 7/8 x 8 7/8 | Reply envelope that fits inside a #10; letter tri-folded |
| #10 | 4 1/8 x 9 1/2 | The standard business envelope: 8.5 x 11 letter tri-folded, 4 x 9 rack cards |
| A2 | 4 3/8 x 5 3/4 | 4.25 x 5.5 cards, RSVP cards, letter folded in quarters |
| A6 | 4 3/4 x 6 1/2 | 4.5 x 6.25 cards, 4 x 6 photos and invitations |
| A7 | 5 1/4 x 7 1/4 | 5 x 7 invitations, announcements and greeting cards |
| A9 | 5 3/4 x 8 3/4 | 5.5 x 8.5 cards, letter folded in half |
| 6 x 9 booklet | 6 x 9 | 5.5 x 8.5 booklets and brochures, letter folded in half |
| 9 x 12 catalog | 9 x 12 | 8.5 x 11 documents flat (unfolded), thin reports |
| 10 x 13 catalog | 10 x 13 | 9 x 12 presentation folders, thicker documents and catalogs |
Choosing the right envelope
- Allow about 1/8"–1/4" of clearance on width and height so inserts slide in easily. The A-series is sized for this: an A7 is 1/4" larger than a 5 x 7 card.
- Thick inserts need more room. For multi-page pieces, booklets or folders, size up or consider a gusseted envelope.
- Booklet vs catalog style: booklet envelopes open on the long side (easier for inserting by machine); catalog envelopes open on the short end.
- Windows: a standard #10 window sits 7/8" from the left and 1/2" from the bottom and is 1 1/8" x 4 1/2". Lay out your letter so the address lines up.
Postage tips
USPS treats pieces up to 6 1/8" x 11 1/2" and 1/4" thick as letters; square envelopes and rigid pieces pay a non-machinable surcharge. Larger envelopes such as 9 x 12 are mailed as flats at a higher rate. Check current USPS rates before a big mailing, or ask our mailing services team.
Frequently asked questions
- What size envelope fits a letter folded in thirds?
- A #10 (4 1/8 x 9 1/2). A #9 also fits and is used as a return envelope inside a #10.
- What envelope fits a 5 x 7 invitation?
- An A7 envelope (5 1/4 x 7 1/4).
- What envelope holds 8.5 x 11 paper without folding?
- A 9 x 12 catalog or booklet envelope. Use 10 x 13 for presentation folders or thicker sets.
Related services
Helpful customer tools
- Folding Guide (shows envelope fit) (available to customers with a free account)
Already a customer? Log in to use them.