Aspect Ratios of Flags that I have used.

Ratio ratio small medium* Countries 11:28 0.3929 - - Qatar 1:2 0.5000 36x18 65x33 69x35 73x37 GB, Russia(pre-1993) (& copies), Croatia, Macedonia, Slovenia, Canada 10:19 0.5263 34x18 - USA 4:7 0.5714 32x18 64x37 Mexico 3:5 0.6000 30x18 61x37 Germany (& copies?), Finland 5:8 0.6250 29x18 57x36 Sweden, Estonia (28x18, 56x37) 2:3 0.6666 27x18 55x37 France (& copies), Hungary, S Korea, Slovakia, Czech, Albania, China, Greece, Russia(post 1993), Austria, Spain, Romania, Netherlands 7:10 0.7000 26x18 51x36 Japan 5:7 0.7143 25x18 50x36 Iceland 8:11 0.7273 25x18 50x36 Norway 28:37 0.7568 24x18 47x36 Denmark 13:15 0.8666 21x18 43x37 Belgium 1:1 1.0000 18x18 37x37 Switzerland

*medium includes 1 px right and below for drop shadow

Check Poland and Estonia's aspect ratios
Poland 36x58,
37x59,
29x18

belarus 1:2

moldova 2:3

bosnia 1:2

estonia 7:11

lithuania 1:2

latvia 1:2