The European paper-size A4 (as defined by the ISO standards) we use in New Zealand, is not the same as an American-sized A4 (practically a mis-nomer, as its only ever called ‘letter’ as far as I'm aware. A3 is called ‘ledger’. I guess they use the other An values)
The area of a European A0 sheet (the largest size) is 1m². An+1, n ∈ [0,7] is half the area, with the proportion of 1:√2. So A4 is 1/2⁴ = 1/16 m².
This may clear up some confusion that is probably out there when you see various programs (most commonly with PDF related software, in my experience) that lists A4 as being 8×11 inches, which is not the same as 210×297 mm (the standard European size).