Formula
The short and long sides come from the square-root-of-two series, then round to the nearest millimetre:
short = round(1,000 × 2^(−1/4 − n/2))
The long side uses +1/4 in the exponent. Bleed around a trim size stays on the bleed page.
Assumptions
- The step is a whole number from 0 to 10.
- Rounding matches the published millimetre sizes.
- The sheet is portrait in the sense that the second number is the long side.
Worked example
A4, which is step 4, is 210 × 297 mm.
Input definitions
- Step
- The A number. A0 is 0 and A4 is 4.
- Sheet
- The short side and the long side in millimetres.
Limitations
This is a planning figure from the numbers you type. It is not a measurement of a network, a camera, a printer, or a power supply.
Questions
Why is A4 210 by 297?
Those are the rounded millimetres of the fourth halving of the A0 sheet.
Does this include letter paper?
No. Letter is 8.5 by 11 inches and is not part of the A series.