This relates to the 'weight' of the paper, and the weight of the paper is closely related to its thickness. Regardless of the size system, you may notice markings such as 'g/m2' or 'gsm' on paper when you buy it. Some Common ISO Envelope Sizes: C Series (+ DL) An additional useful envelope size is the long-format 'DL' envelope designed to accommodate A4 paper folded in three. A5 paper (or A4 folded in two) fits neatly into a C5 envelope.

Thus A4 paper fits neatly into a C4 envelope. For each A size there is a slightly larger 'C' size for envelopes. The International paper system specifies envelope sizes based on the A paper sizes. Sizes smaller than A6 (A7, A8 etc) exist for such things as very small notepads, visiting cards etc. Sizes larger than A3 exist but are rarely used by the general public. It is often used in card form rather than paper, and is the size of many: Note that some items (greetings cards for example) may be A5 in size but actually made from A4 paper folded in two.Ī6 is half the size of A5 and quarter the size of A4. A5: 148 x 210 mmĪ5 paper is half the size of A4. Note that some items (brochures for example) may be A4 in size but actually made from A3 paper folded in two. It is typically used for:Ī4 is the most commonly used International paper size. It is possible to buy A3 photocopy paper, though not all photocopiers/printers can handle it. The most common A paper sizes are: A3: 297 x 410 mmĪ3 paper is quite large. The metric dimensions are also often converted into imperial units-inches (in or '). The International ISO system is based on metric units-millimetres (mm) and centimetres (cm). The important thing is that each A size has the same proportions or 'shape': 1 is to the When folded in two, A3 becomes A4, A4 becomes A5, and so on. The eagle-eyed among you will spot a fourth format: A2.

This diagram shows three formats from the ISO A series: A3, A4 and A5.

The system was developed in Germany in the early 1920s and then spread internationally. International system (ISO)Īlso 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). So 8 x 10 is vertical (also known as portrait) and 10 x 8 is horizontal (also known as landscape). Note that paper sizes are measured as width first x height second.

A2 size in cm