9 x 12 inches and 11 x 14 inches are standard in art paper in the US. As are 5 x 7 and 8 x 10. The first one, 9 x 12, happens to also be “ARCH A” but I haven’

9 x 12 inches and 11 x 14 inches are standard in art paper in the US. As are 5 x 7 and 8 x 10. The first one, 9 x 12, happens to also be “ARCH A” but I haven’t seen a fancy name for the others.