Envelope Size Chart: Standard Envelope Sizes in Inches and mm
The most used envelope sizes are the #10 business envelope at 4 1/8 x 9 1/2 inches for letter paper folded in thirds, the 6 x 9 catalog envelope for paper folded in half, the 9 x 12 and 10 x 13 catalog envelopes for unfolded 8 1/2 x 11 documents, and the A7 at 5 1/4 x 7 1/4 inches for 5 x 7 cards. Envelope sizes are listed height by length, with the short side first. The charts below give every standard size in inches and millimeters, what it fits, and how USPS classifies it.
Business envelope sizes
Business envelopes, also called commercial envelopes, open on the long side and carry folded letters, invoices and statements. The number is a trade size, not a measurement.
| Size | Inches | Millimeters | Fits | USPS shape | Stock |
|---|---|---|---|---|---|
| #6 3/4 | 3 5/8 x 6 1/2 | 92 x 165 | Personal letters, remittance and invoice returns | Letter | |
| #7 3/4 Monarch | 3 7/8 x 7 1/2 | 98 x 190 | Personal stationery and executive letterhead | Letter | |
| #9 | 3 7/8 x 8 7/8 | 98 x 225 | Reply envelope that fits inside a #10 | Letter | |
| #10 | 4 1/8 x 9 1/2 | 105 x 241 | Letter paper folded in thirds: the standard business envelope | Letter | Stocked |
| #11 | 4 1/2 x 10 3/8 | 114 x 264 | Thicker tri-folded letters and statements | Letter | |
| #12 | 4 3/4 x 11 | 121 x 279 | Bulky tri-folded mail | Letter | |
| #14 | 5 x 11 1/2 | 127 x 292 | Legal paper folded in thirds | Letter |
Catalog envelope sizes
Catalog envelopes open on the short end, so documents slide in flat and stay put. They come with a gummed flap, a self-seal or peel-and-seal strip, or a metal clasp for reuse, and in tear-resistant Tyvek for documents that travel far.
| Size | Inches | Millimeters | Fits | USPS shape | Stock |
|---|---|---|---|---|---|
| #1 | 6 x 9 | 152 x 229 | Letter paper folded in half, booklets | Letter | Stocked in 4 styles |
| #1 3/4 | 6 1/2 x 9 1/2 | 165 x 241 | Half-folded letter paper with room to spare | Flat | Stocked |
| #3 | 7 x 10 | 178 x 254 | Small catalogs and half-folded statements | Flat | |
| #6 | 7 1/2 x 10 1/2 | 190 x 267 | Booklets and small catalogs | Flat | Stocked |
| #8 | 8 1/4 x 11 1/4 | 210 x 286 | Unfolded half-sheet stacks and small catalogs | Flat | |
| #9 3/4 | 8 3/4 x 11 1/4 | 222 x 286 | Snug fit for unfolded letter paper | Flat | |
| #10 1/2 | 9 x 12 | 229 x 305 | Unfolded 8 1/2 x 11 letter paper: the most common large envelope | Flat | Stocked in 4 styles |
| #12 1/2 | 9 1/2 x 12 1/2 | 241 x 318 | Letter paper with extra room for thicker stacks | Flat | Stocked in 4 styles |
| #13 1/2 | 10 x 13 | 254 x 330 | Thick documents and 9 x 12 pocket folders | Flat | Stocked in 4 styles |
| #14 1/2 | 11 1/2 x 14 1/2 | 292 x 368 | Legal paper, annual reports and catalogs | Flat | Stocked in 2 styles |
| #15 | 10 x 15 | 254 x 381 | Unfolded legal paper | Flat | Stocked in 2 styles |
| #15 1/2 | 12 x 15 1/2 | 305 x 394 | Oversized catalogs and bulky document sets | Parcel | Stocked in 3 styles |
9 x 12 or 10 x 13? A 9 x 12 envelope takes a stack of letter paper with a little room to spare. Step up to 9 1/2 x 12 1/2 for thicker stacks and to 10 x 13 for a 9 x 12 pocket folder or a stack more than about half an inch thick.
Card and invitation envelope sizes
A-style envelopes are sized for greeting cards, invitations and photos, with a square flap and a little clearance around the card.
| Size | Inches | Millimeters | Fits | USPS shape |
|---|---|---|---|---|
| A2 | 4 3/8 x 5 3/4 | 111 x 146 | 4 1/4 x 5 1/2 cards and invitations | Letter |
| A6 | 4 3/4 x 6 1/2 | 121 x 165 | 4 x 6 photos and cards | Letter |
| A7 | 5 1/4 x 7 1/4 | 133 x 184 | 5 x 7 invitations, photos and cards | Letter |
| A8 | 5 1/2 x 8 1/8 | 140 x 206 | 5 1/4 x 7 7/8 cards | Letter |
| A9 | 5 3/4 x 8 3/4 | 146 x 222 | Half-letter 5 1/2 x 8 1/2 cards and folded letter paper | Letter |
| A10 | 6 x 9 1/2 | 152 x 241 | 5 3/4 x 9 1/4 cards and programs | Letter |
Coin envelope sizes
Coin envelopes are small kraft envelopes that open on the short end. Offices use them for cash and keys, shops for small parts and spare hardware, and growers for seeds.
| Size | Inches | Millimeters | Fits | Stock |
|---|---|---|---|---|
| #1 | 2 1/4 x 3 1/2 | 57 x 89 | Coins, keys, seeds and small parts | Stocked |
| #3 | 2 1/2 x 4 1/4 | 64 x 108 | Payroll cash, small parts and seeds | Stocked |
| #4 | 3 x 4 1/2 | 76 x 114 | Small parts and samples | |
| #5 1/2 | 3 1/8 x 5 1/2 | 79 x 140 | Coins, stamps and spare buttons | Stocked |
| #6 | 3 3/8 x 6 | 86 x 152 | Cash, receipts and replacement parts | Stocked |
| #7 | 3 1/2 x 6 1/2 | 89 x 165 | Bank deposits and cash envelopes | Stocked |
Large and jumbo envelopes
Jumbo envelopes hold artwork, blueprints, posters shipped flat and large document sets. Every size here is larger than the USPS flat limit, so it mails at parcel prices.
| Size, in | Millimeters | Material | USPS shape |
|---|---|---|---|
| 12 1/2 x 18 1/2 | 318 x 470 | 28 lb kraft | Parcel |
| 14 x 18 | 356 x 457 | 28 lb kraft | Parcel |
| 13 x 19 | 330 x 483 | Tyvek | Parcel |
| 15 x 20 | 381 x 508 | Tyvek | Parcel |
| 15 x 20 | 381 x 508 | 28 lb kraft | Parcel |
| 16 x 20 | 406 x 508 | 28 lb kraft | Parcel |
| 17 x 22 | 432 x 559 | 28 lb kraft | Parcel |
| 18 x 23 | 457 x 584 | 28 lb kraft | Parcel |
| 18 x 23 | 457 x 584 | Tyvek | Parcel |
| 24 x 30 | 610 x 762 | 28 lb kraft | Parcel |
| 24 x 36 | 610 x 914 | 28 lb kraft | Parcel |
| 22 x 27 | 559 x 686 | 28 lb kraft | Parcel |
International envelope sizes
| Size | Millimeters | Inches | Fits |
|---|---|---|---|
| DL | 110 x 220 | 4.33 x 8.66 | A4 folded in thirds |
| C6 | 114 x 162 | 4.49 x 6.38 | A4 folded in quarters, A6 cards |
| C5 | 162 x 229 | 6.38 x 9.02 | A4 folded in half, A5 sheets |
| C4 | 229 x 324 | 9.02 x 12.76 | A4 sheets unfolded |
USPS letter, flat and parcel size limits
USPS prices an envelope by its shape. A letter is 3 1/2 to 6 1/8 inches high, 5 to 11 1/2 inches long and no more than 1/4 inch thick. A flat, which USPS also calls a large envelope, can be up to 12 inches high, 15 inches long and 3/4 inch thick, and must be flexible and uniformly thick. Anything larger, thicker or rigid mails as a parcel.
- A #10 and a 6 x 9 envelope mail as letters when they are 1/4 inch thick or less.
- 9 x 12, 9 1/2 x 12 1/2, 10 x 13, 11 1/2 x 14 1/2 and 10 x 15 envelopes mail as flats.
- A 12 x 15 1/2 envelope is longer than 15 inches, so it mails as a parcel even when it holds a few sheets.
- Square envelopes and lumpy contents such as keys or pens can trigger the nonmachinable surcharge on letters.
Shop envelopes by size
- All mailing envelopes: kraft, white and Tyvek catalog envelopes, clasp envelopes, #10 security envelopes, coin envelopes, expandable envelopes and jumbo envelopes.
- 9 x 12 kraft self-seal envelopes and 10 x 13 kraft self-seal envelopes, 500 per case.
- 9 x 12 Tyvek envelopes for tear-resistant document mailing.
- 9 x 12 x 2 expandable envelopes for thick files and binders.
Frequently asked questions
What is the standard envelope size?
The #10 business envelope, 4 1/8 x 9 1/2 inches, is the standard size for letters folded in thirds. For unfolded documents the standard is the 9 x 12 inch catalog envelope.
What size envelope fits 8 1/2 x 11 paper without folding?
A 9 x 12 inch envelope. Use 9 1/2 x 12 1/2 for a thicker stack and 10 x 13 for a pocket folder or more than about half an inch of paper.
What size envelope for a 5 x 7 card?
An A7 envelope, 5 1/4 x 7 1/4 inches, which leaves about 1/8 inch of clearance on each side.
What size is a #10 envelope in mm?
About 105 x 241 mm. In inches it is 4 1/8 x 9 1/2.
Is a 9 x 12 envelope a letter or a flat?
A flat. USPS letters max out at 6 1/8 x 11 1/2 inches, so a 9 x 12 envelope mails at the large envelope price up to 3/4 inch thick.
How are envelope sizes measured?
Height by length, short side first, measured on the closed envelope. A 6 x 9 envelope is 6 inches high and 9 inches long.
What is the difference between catalog and booklet envelopes?
Catalog envelopes open on the short end and booklet envelopes open on the long side. Booklet envelopes run through inserting machines; catalog envelopes hold contents more securely in the mail.
What envelope fits A4 paper?
C4, 229 x 324 mm, for A4 flat. In US sizes, a 9 1/2 x 12 1/2 or 10 x 13 inch envelope also fits an unfolded A4 sheet.
Related tools and charts
- Mailer size chart: bubble, poly and corrugated
- Poly mailer size chart
- Packing list envelope sizes
- USPS flat rate box and envelope sizes
- All mailing envelopes
USPS shape limits follow the Domestic Mail Manual, section 101. Millimeters are rounded to the nearest whole millimeter.