Frame size guide
Here is a guide so you can compare some of the most popular frame sizes in the US:
16x20 inches = 40.64 x 50.8 cm
11x14 inches = 27.94 x 35.56 cm
8x10 inches = 20.32 x 25.4 cm
5x7 inches = 12.7 x 17.78 cm
ISO sizes
Some countries like Australia and some countries in Europe use the following sizes:
A2 = 16.54 x 23.36 inches = 594 x 420 mm
A3 = 11.69 x 16.54 inches = 420 x 297 mm
A4 = 8.27 x 11.69 inches = 297 x 210 mm
A5 = 5.83 x 8.27 inches = 210 x 148 mm