Paper Sizes Vocabulary

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Paper sizes around the world are divided mostly into:

1. The International system (ISO)
   Most countries worldwide (except USA and Canada)
2. The North American system (ANSI)
   Mostly USA and Canada

1. International system (ISO)

Also known as the "A Series" and "ISO 216", the system is such that when folded in two all A sizes retain their proportions, which are 1 to the square root of 2 (1:√2 or approximately 1:1.4). This makes A sizes easy to scale. The system was developed in Germany in the early 1920s and then spread internationally.

This diagram shows three formats from the ISO A series: A3, A4 and A5. The eagle-eyed among you will spot a fourth format: A2. When folded in two, A3 becomes A4, A4 becomes A5, and so on. The important thing is that each A size has the same proportions or "shape": 1 is to the √2.

The International ISO system is based on metric units—millimetres (mm) and centimetres (cm). The metric dimensions are also often converted into imperial units—inches (in or ").

Paper

The most common A paper sizes are:

A3: 297 x 410 mm

A3 paper is quite large. It is possible to buy A3 photocopy paper, though not all photocopiers/printers can handle it. It is typically used for:

• small posters
• drawings
• artwork

A4: 210 x 297 mm

A4 is the most commonly used International paper size. This is the size used for most:

• photocopy paper
• business letters
• legal/official documents
• student notepads
• brochures, flyers

Note that some items (brochures for example) may be A4 in size but actually made from A3 paper folded in two.

A5: 148 x 210 mm

A5 paper is half the size of A4. This is the size of many:

• private letters, invitations
• commercial memos
• small notepads
• organizers, diaries
• small brochures, flyers
• greetings cards

Note that some items (greetings cards for example) may be A5 in size but actually made from A4 paper folded in two.

A6: 105 x 148 mm

A6 is half the size of A5 and quarter the size of A4. It is often used in card form rather than paper, and is the size of many:

• invitation cards
• greetings cards

Other A sizes

Sizes larger than A3 exist but are rarely used by the general public. Sizes smaller than A6 (A7, A8 etc) exist for such things as very small notepads, visiting cards etc.

Envelopes

The International paper system specifies envelope sizes based on the A paper sizes. For each A size there is a slightly larger "C" size for envelopes. Thus A4 paper fits neatly into a C4 envelope. A5 paper (or A4 folded in two) fits neatly into a C5 envelope. An additional useful envelope size is the long-format "DL" envelope designed to accommodate A4 paper folded in three.

2. North American system (ANSI)

Paper sizes in the USA, Canada and Mexico (and the Philippines and Chile) are based on traditional sizes, which are difficult to scale. Since 1995, North American sizes have often been prefaced with "ANSI" (American National Standards Institute). The most commonly used North American paper size is Letter (8.5" x 11").

The ANSI system is based on imperial units—inches (in or "). The imperial units are also often converted into metric units—millimetres (mm) and centimetres (cm).

Note that International paper sizes are increasingly available and used in North America.

Paper

The most common ANSI paper sizes are:

Tabloid: 11 x 17 in (portrait) / Ledger: 17 x 11 in (landscape)

Tabloid and Ledger sizes have the same dimensions but a different orientation. Tabloid is "portrait" or vertical, while Ledger is "landscape" or horizontal. They are both typically used for small posters, flyers, brochures, drawings, diagrams and large tables. Note that Ledger can fold in two to make Letter size.

Legal: 8.5 x 14 in

Legal size paper is typically used for legal documents, flyers and brochures.

Letter: 8.5 x 11 in

Letter size paper is the most commonly used ANSI paper size. It is close to the ISO A4 size, and is typically used in North America for:

• photocopy paper
• business letters
• student notepads
• brochures, flyers

Half Letter: 5.5 x 8.5 in

Half Letter is the same as Letter size folded in two. It is close to the ISO A5 size, and is typically used for private letters, invitations, flyers, postcards, small notepads, greetings cards, organizers and diaries. Also known as Statement, Stationery, Memo, Half Size and Half A.

Architectural sizes

This range of larger sizes is typically used by architects and draughtsmen, and seldom used directly by the general public.

Envelopes

There are dozens of envelope sizes for North America, and several different "styles" of envelope relating to the shape, material and strength. The most common styles are Commercial (mainly for office and business use), Announcement (more for personal use) and Catalog (for catalogues, brochures and heavier contents). Of Commercial envelopes, "No.10" is the standard business size envelope accommodating Letter size paper folded in three or Legal size paper folded in four (close to the long-format ISO DL envelope).

Recommended links

PaperSizes.io

Paper Sizes and Formats Explained

A size chart illustrating the ISO A series

Envelope Styles and Sizes

North American Paper & Envelope Sizes