Each is half the area of the one before, ie A4 paper (297 mm × 210 mm) is half the size of A3 paper (297 mm × 420 mm).

International A series paper size formats from A0 to A10, including the most popular A3, A4 and A5 formats. International A series paper size formats from A0 to A10, including the most popular A3, A4 ...

The Verdict: On paper, the A4 may not appear to be much larger than the A3, but in reality, the A4 is a larger vehicle. The A3 has four doors, but despite its size, the A4 is a better option if you ...