Manila envelope sizes run from 6×9 inches (152.4 x 228.6 mm) to 12×15.5 inches (304.8 x 393.7 mm). The most common size is 9×12 inches (228.6 x 304.8 mm), which fits a US Letter sheet flat. Larger manila envelope sizes like 10×15 inches (254.0 x 381.0 mm) fit legal paper flat, while smaller ones like 6×9 hold a letter folded once.
A manila envelope is the stiff, tan-colored envelope you see in offices, schools and mailrooms everywhere. It is made from heavy manila paper, which is thicker and stronger than the paper used for a normal letter envelope, so it protects documents, photos and certificates without bending them. Sizes are written as width x height in inches, for example 9×12 means 9 inches wide and 12 inches tall. This guide covers every standard size in the manila envelope sizes range, what fits in each one, and how to pick the right size for mailing, filing or storing documents.
Manila Envelope Sizes at a Glance
| Envelope Size | Inches (W x H) | Centimeters | Millimeters | Fits Flat |
|---|---|---|---|---|
| 6×9 | 6 x 9 in | 15.24 x 22.86 cm | 152.4 x 228.6 mm | Half-letter (5.5 x 8.5 in), US Letter folded once |
| 9×12 | 9 x 12 in | 22.86 x 30.48 cm | 228.6 x 304.8 mm | US Letter flat, A4 flat, 8×10 photo |
| 9.5×12.5 | 9.5 x 12.5 in | 24.13 x 31.75 cm | 241.3 x 317.5 mm | US Letter flat, A4 flat, legal folded once |
| 10×13 | 10 x 13 in | 25.4 x 33.02 cm | 254.0 x 330.2 mm | US Letter flat, file folder flat, legal folded once |
| 10×15 | 10 x 15 in | 25.4 x 38.1 cm | 254.0 x 381.0 mm | Legal paper flat, US Letter flat, file folder |
| 12×15.5 | 12 x 15.5 in | 30.48 x 39.37 cm | 304.8 x 393.7 mm | Legal paper flat, file folder, large documents |
| #10 (business) | 4.125 x 9.5 in | 10.48 x 24.13 cm | 104.8 x 241.3 mm | US Letter folded in thirds |
Quick tip: envelope sizes are always written as width x height, and the paper inside must be smaller than the envelope on both sides. A US Letter sheet is 8.5 x 11 inches, so it fits flat only in an envelope that is at least 9 inches wide and 12 inches tall — that is why the 9×12 is the most common size in the manila envelope sizes range.
What Is a Manila Envelope?
A manila envelope is a large, stiff envelope made from manila paper, a strong, light-brown paper originally made from Manila hemp. The paper is much thicker than ordinary printer paper, usually around 24 to 28 lb stock, which is why a manila envelope holds its shape, protects the papers inside from bending, and survives being carried, filed and mailed. Most manila envelopes have a metal clasp and a gummed flap, so you can seal them, open them again, and reseal them without tearing the paper.
Manila envelopes are used for mailing documents that must not be folded, like certificates, contracts and photos, and for storing papers flat in a drawer or on a shelf. They come in the standard manila envelope sizes listed in the chart above, from the small 6×9 up to the large 12×15.5. The size you need depends on what goes inside: a single letter fits in a 6×9 when folded once, a full letter fits flat in a 9×12, and legal paper needs a 10×15 or larger to stay flat.
Catalog vs Booklet: Two Kinds of Manila Envelopes
Manila envelopes come in two opening styles, catalog and booklet, and the difference matters when you put papers in and take them out. A catalog envelope opens on the short side, so the flap runs along the short top edge and you slide papers in from the top, like putting a letter into a pocket. A booklet envelope opens on the long side, so the flap runs along the long edge and you slide papers in from the side, like opening a book.
Catalog envelopes are the ones most people picture when they think of manila envelope sizes: the classic 9×12, 10×13 and 12×15.5 envelopes are usually catalog style, with the clasp on the short top edge. Booklet envelopes are common in the smaller sizes, like 6×9 and 9×12, and they are handy when you need to pull a thick stack of papers out sideways without bending the corners. The US Postal Service treats a 9×12 manila envelope as a large envelope, also called a flat, which costs more to mail than a normal letter but less than a package.
Manila Envelope Sizes Chart
The full manila envelope sizes chart covers seven standard sizes. Each size is listed below with its exact dimensions in inches, centimeters and millimeters, and what fits inside it. All dimensions are width x height, measured on the outside of the envelope.
6×9 inches (15.24 x 22.86 cm, 152.4 x 228.6 mm). The smallest standard size in the manila envelope sizes range. It holds a half-letter sheet (5.5 x 8.5 inches) flat, or a US Letter sheet folded once, which also measures 5.5 x 8.5 inches. It is the right size for greeting cards, small photos and half-sheet forms. It does not fit a full US Letter sheet flat, because the sheet is 8.5 inches wide and 11 inches tall, and the envelope is only 6 inches wide.
9×12 inches (22.86 x 30.48 cm, 228.6 x 304.8 mm). The most common size, and the one most offices keep in stock. It fits a US Letter sheet (8.5 x 11 inches) flat with about half an inch to spare on each side, and it fits an A4 sheet (210 x 297 mm, or 8.27 x 11.69 inches) flat as well. An 8×10 photo print (203.2 x 254.0 mm) and a standard magazine (8.5 x 11 inches) also fit flat. This is the size to buy if you only want to keep one size on hand.
9.5×12.5 inches (24.13 x 31.75 cm, 241.3 x 317.5 mm). A slightly roomier version of the 9×12, with half an inch extra in each direction. It fits US Letter and A4 flat, and it fits legal paper folded once, which measures 7 x 8.5 inches after folding. It does not fit legal paper flat, because legal paper is 14 inches tall and the envelope is only 12.5 inches tall. This size is useful when the papers inside are thick, or when you want a little extra room around a 9×12 document.
10×13 inches (25.4 x 33.02 cm, 254.0 x 330.2 mm). The first size in the manila envelope sizes range that fits a manila file folder flat. A standard manila file folder measures 9.5 x 11.75 inches (241.3 x 298.4 mm), so it slides into a 10×13 with room to spare. It also fits US Letter and A4 flat, and legal paper folded once. Like the 9.5×12.5, it does not fit legal paper flat, because legal paper is 14 inches tall and the envelope is 13 inches tall.
10×15 inches (25.4 x 38.1 cm, 254.0 x 381.0 mm). The largest common size, and the smallest size that fits legal paper flat. Legal paper is 8.5 x 14 inches (215.9 x 355.6 mm), so it fits inside a 10×15 with 1.5 inches to spare in width and 1 inch in height. It also fits US Letter, A4, magazines and file folders flat. If you mail legal documents and do not want to fold them, this is the size to use.
12×15.5 inches (30.48 x 39.37 cm, 304.8 x 393.7 mm). The biggest size in the standard manila envelope sizes range. It fits legal paper flat with plenty of room, and it fits file folders, large catalogs and oversized documents that are too big for a 10×15. It is the size used for mailing thick reports, large certificates and stacks of legal papers that need to stay flat and unbent.
#10 business envelope (4.125 x 9.5 inches, 10.48 x 24.13 cm, 104.8 x 241.3 mm). The #10 is the standard business envelope, not a large manila envelope, but it belongs in the manila envelope sizes chart because it is the size most letters are mailed in. It fits a US Letter sheet folded in thirds, which measures about 3.7 x 8.5 inches after folding. It is too small for anything that must stay flat.
What Fits in Each Size? Everyday Size Comparisons
A size in inches is hard to picture on its own. Here is how each of the standard manila envelope sizes compares with the everyday things you actually put inside them. Each comparison below uses one of the six everyday items assigned to this guide, so you can picture the fit before you buy.
US Letter Paper (8.5 x 11 in)
US Letter paper measures 8.5 x 11 inches (215.9 x 279.4 mm), and it is the paper most printers in the United States use. It fits flat in a 9×12 envelope with about half an inch to spare on each side, which is why the 9×12 is the standard envelope for mailing letters, resumes and contracts that must not be folded. It also fits flat in the 9.5×12.5, 10×13, 10×15 and 12×15.5 sizes. In a 6×9 envelope it only fits folded once, which makes it 5.5 x 8.5 inches. If you mail letters every day, the 9×12 is the size to keep in stock, because it is the smallest of the manila envelope sizes that takes a full letter flat.
Legal Paper (8.5 x 14 in)
Legal paper measures 8.5 x 14 inches (215.9 x 355.6 mm), which is 3 inches taller than US Letter paper. It fits flat only in the two largest manila envelope sizes: the 10×15, which leaves 1 inch of room above the paper, and the 12×15.5, which leaves 1.5 inches. In a 10×13 envelope the paper is 1 inch too tall, so it does not fit flat, and in a 9.5×12.5 it is 1.5 inches too tall. Folded once, legal paper measures 7 x 8.5 inches and fits in a 9.5×12.5 or a 10×13 with room to spare. If you work with legal documents, buy the 10×15, because it is the smallest size that keeps legal paper flat and uncreased.
Magazine (8.5 x 11 in)
A standard magazine measures about 8.5 x 11 inches (215.9 x 279.4 mm), the same size as a US Letter sheet. It fits flat in a 9×12 envelope, which is the size most people use for mailing a single magazine, and it fits flat in every larger size in the manila envelope sizes range. A thick magazine with many pages may need the 9.5×12.5 or the 10×13, because the extra half inch of width gives the pages room to slide in without bending the corners. A 6×9 envelope is far too small for a magazine, because the magazine is 2.5 inches wider than the envelope.
8×10 Photo Print (8 x 10 in)
An 8×10 photo print measures 8 x 10 inches (203.2 x 254.0 mm), and it fits flat in a 9×12 envelope with 1 inch to spare on each side, which protects the corners of the print. It also fits flat in the 9.5×12.5, 10×13, 10×15 and 12×15.5 sizes. It does not fit in a 6×9 envelope, because the print is 2 inches wider and 1 inch taller than the envelope. For mailing photos, a 9×12 is the usual choice, and a stiff backing board inside the envelope keeps the print from bending in the mail.
Paperback Book (About 8 x 5.5 in)
A typical paperback book measures about 8 x 5.5 inches (203.2 x 139.7 mm), though paperbacks vary from about 6.5 to 9 inches tall. A small paperback fits flat in a 9×12 envelope, and a thicker paperback with 300 or more pages fits better in a 10×13, because the extra width gives the spine room. A 6×9 envelope fits only a very small paperback, and only if the book is no wider than 5.5 inches and no taller than 8.5 inches. For mailing a paperback, the 9×12 is the usual size, and the 10×13 is the safer choice for a thick book.
Manila File Folder (9.5 x 11.75 in)
A standard manila file folder measures 9.5 x 11.75 inches (241.3 x 298.4 mm), which makes it too wide for a 9×12 envelope, because the folder is half an inch wider than the envelope. The smallest size in the manila envelope sizes range that fits a file folder flat is the 10×13, which leaves half an inch of room on each side. The 10×15 and 12×15.5 also fit a folder flat, with more room to spare. If you need to mail a folder with its papers still inside, use a 10×13, because the folder keeps the papers in order and the envelope keeps the folder from bending.
How to Choose the Right Manila Envelope Size
Picking the right size from the manila envelope sizes range is simple once you know what goes inside. Start by measuring the largest thing that must stay flat, then pick the smallest envelope that is bigger than it on both sides. That keeps the envelope small enough to mail cheaply and big enough to protect the contents.
For mailing a letter or a few pages. Use a 9×12 for papers that must stay flat, or a 6×9 if you are happy to fold the letter once. A 9×12 costs more to mail than a normal #10 letter envelope, because the US Postal Service classes it as a large envelope, but it keeps the letter flat and looking professional.
For mailing legal paper. Use a 10×15 if the paper must stay flat, or a 9.5×12.5 if you can fold it once. Do not use a 10×13 for legal paper you want to keep flat, because the paper is 14 inches tall and the envelope is only 13 inches tall, so the paper will not fit.
For mailing photos or certificates. Use a 9×12 for an 8×10 photo or a standard certificate, and add a stiff backing board so the print does not bend. For a larger certificate or a thick stack of photos, use a 10×13, because the extra room stops the corners from bending when the envelope is handled.
For filing and storage. Use a 10×13 for a manila file folder, because it is the smallest size that fits a folder flat. Use a 12×15.5 for thick folders or for papers that are already in a folder with extra pages clipped inside.
Manila Envelope Sizes in Inches and Centimeters
Envelope sizes are listed in inches in the United States, but many buyers need the size in centimeters or millimeters, especially when ordering online or matching a size from another country. The table below converts every measurement in the manila envelope sizes range from inches to centimeters and millimeters, using 1 inch = 2.54 cm = 25.4 mm exactly.
| Inches | Centimeters | Millimeters |
|---|---|---|
| 4.125 in | 10.48 cm | 104.8 mm |
| 6 in | 15.24 cm | 152.4 mm |
| 8.5 in | 21.59 cm | 215.9 mm |
| 9 in | 22.86 cm | 228.6 mm |
| 9.5 in | 24.13 cm | 241.3 mm |
| 10 in | 25.4 cm | 254.0 mm |
| 12 in | 30.48 cm | 304.8 mm |
| 12.5 in | 31.75 cm | 317.5 mm |
| 13 in | 33.02 cm | 330.2 mm |
| 14 in | 35.56 cm | 355.6 mm |
| 15 in | 38.1 cm | 381.0 mm |
| 15.5 in | 39.37 cm | 393.7 mm |
Quick tip: to convert any envelope size yourself, multiply the inches by 2.54 to get centimeters, or by 25.4 to get millimeters. For example, a 9×12 envelope is 9 x 2.54 = 22.86 cm wide and 12 x 2.54 = 30.48 cm tall.
Paper sizes use the same conversions. US Letter paper is 8.5 x 11 inches, which is 215.9 x 279.4 mm. Legal paper is 8.5 x 14 inches, which is 215.9 x 355.6 mm. A4 paper is 210 x 297 mm, which is 8.27 x 11.69 inches, so it fits flat in a 9×12 envelope with room to spare. A manila file folder is 9.5 x 11.75 inches, which is 241.3 x 298.4 mm, so it needs a 10×13 envelope or larger.
Frequently Asked Questions
What is the most common manila envelope size?
The most common of all manila envelope sizes is the 9×12 inch envelope (22.86 x 30.48 cm, 228.6 x 304.8 mm). It fits a US Letter sheet and an A4 sheet flat, it fits an 8×10 photo and a standard magazine flat, and it is the size most offices keep in stock. If you only buy one size, buy the 9×12.
What size envelope fits a US Letter paper flat?
A 9×12 inch envelope is the smallest size that fits a US Letter sheet flat. US Letter paper is 8.5 x 11 inches, so it needs an envelope at least 9 inches wide and 12 inches tall. The 9.5×12.5, 10×13, 10×15 and 12×15.5 sizes also fit it flat. A 6×9 envelope only fits a US Letter sheet folded once, which makes it 5.5 x 8.5 inches.
What size envelope fits legal paper?
A 10×15 inch envelope is the smallest size that fits legal paper flat. Legal paper is 8.5 x 14 inches, so it needs an envelope at least 10 inches wide and 15 inches tall. The 12×15.5 also fits it flat. A 9.5×12.5 or a 10×13 envelope fits legal paper folded once, but not flat, because legal paper is 14 inches tall and those envelopes are only 12.5 and 13 inches tall.
What is the difference between catalog and booklet envelopes?
A catalog envelope opens on the short side, so the flap runs along the short top edge and you slide papers in from the top. A booklet envelope opens on the long side, so the flap runs along the long edge and you slide papers in from the side. Most large manila envelope sizes, like the 9×12, 10×13 and 12×15.5, are catalog style, while smaller sizes like the 6×9 are often booklet style.
How big is a 9×12 envelope in cm?
A 9×12 envelope is 22.86 x 30.48 centimeters, or 228.6 x 304.8 millimeters. The 9 inches of width converts to 22.86 cm, and the 12 inches of height converts to 30.48 cm. It fits a US Letter sheet (21.59 x 27.94 cm) flat with about 1.27 cm to spare on each side.
Conclusion
Manila envelope sizes run from 6×9 inches (152.4 x 228.6 mm) to 12×15.5 inches (304.8 x 393.7 mm), and the right size depends on what goes inside. The 9×12 is the most common size because it fits a US Letter sheet, an A4 sheet, an 8×10 photo and a magazine flat. The 10×13 is the smallest size that fits a manila file folder flat, and the 10×15 is the smallest size that fits legal paper flat. Remember that manila envelope sizes are written as width x height, and that catalog envelopes open on the short side while booklet envelopes open on the long side. Measure the largest thing that must stay flat, pick the smallest envelope that is bigger than it on both sides, and your documents will arrive flat, safe and looking professional.
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Hi, I’m Michael Carter, I write simple, everyday size guides so you can picture any measurement in seconds.