This document provides the dimensions of A3 paper size in millimetres, centimetres, inches, and pixels. A3 paper measures 297mm by 420mm, 29.7cm by 42cm, 11.7 inches by 16.5 inches, and 3508 pixels by 4962 pixels at 300 pixels per inch. It also notes that A3 size is similar to US Ledger size.