Paper Size Converter

ISO 216 defines the A-series paper sizes (A4, A3, A0. ) using a √2:1 ratio so each size is exactly half the area of the one above

The calculator uses the standard published formula for paper size. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

This calculator works with inches, square metres. You can enter values in the units shown — the calculator handles all conversions internally.

The core formula is: A0 = 841×1189mm (exactly 1m² area). Each step in the calculation is shown so you can verify the result manually.