### From Draftsperson.net

Written by Allan

Created 2-July-2004

## Metric ISO Sheets

- The ratio length to width of ISO sheets is 1 : Square Root 2. A square root is a number that when multiplied by itself will produce the given number (the square).
- An A0 sheet is 1m². This allows paper weights to be expressed in grams per square meter. Example: 110gsm paper.
- This relationship of 1: Sq root 2 is particularly important for reduction onto microfilm, or reduction and enlargement on photocopiers. All metric equipment including microfilm cameras, microfilm printers, photocopiers, and even drawing pen sizes, are designed around this ratio. This makes the process of archiving drawings, resizing, and modifying drawings easy.
- Each smaller sheet size is exactly half the area of the previous size. If you cut an A0 sheet in half you get two A1 sheets; If you cut an A1 sheet in half you get two A2 sheets; and so on ...
- The standard widths for rolls is 860 mm and 610 mm.
- ISO is an acronym for International Organization for Standardization
- * Oversize sheets are used when it is desirable to give extra protection to the drawing sheets by providing a binding or trimming margin.

Cut Sizes of Metric

ISO Sheets
**Designation** |
**Width (mm)** |
**Length (mm)** |

A0 |
841 |
1189 |

A1 |
594 |
841 |

A2 |
420 |
594 |

A3 |
297 |
420 |

A4 |
210 |
297 |

A5 |
149 |
210 |

B1 |
707 |
1000 |

B2 |
500 |
707 |

B3 |
353 |
500 |

B4 |
250 |
253 |