What is difference between A3 and A4? Posted on August 16, 2022 By admin_zxviwxhy The A3 size print measures 29.7 x 42.0cm, 11.69 x 16.53 inches, if mounted 40.6 x 50.8cm, 15.98 x 20 inches. The A4 size print measures 21.0 x 29.7cm, 8.27 x 11.69 inches, if mounted 30.3 x 40.6cm, 11.93 x 15.98 inches.