The British (BS) and International (ISO) Standards give us a range of standard paper sizes to choose from.
The range is know as the ‘A’ Size range. The Largest commonly used size is A0 which is a piece of paper 1m² in area with the sides in proportion 1:√2 (≈ 1:1.4).
A1 is half this size, A2 is half that, A3 is half again and A4 is half that. A4 is the smallest commonly used size for technical drawings.
Table of sizes
| DESIGNATION | LENGTH | WIDTH |
| A0 | 1189 | 841 |
| A1 | 841 | 594 |
| A2 | 594 | 420 |
| A3 | 420 | 297 |
| A4 | 297 | 210 |
Table of enlargement and reduction scales
| FROM / TO | A0 | A1 | A2 | A3 | A4 |
| A0 | 100% | 71% | 50% | 35% | 25% |
| A1 | 141% | 100% | 71% | 50% | 35% |
| A2 | 200% | 141% | 100% | 71% | 50% |
| A3 | 283% | 200% | 141% | 100% | 71% |
| A4 | 400% | 283% | 200% | 141% | 100% |