A3 Paper vs A4 Paper

The A3 Paper and A4 Paper are most easily told apart by their overall size. On height, the A3 Paper measures 420.0 mm against the A4 Paper's 297.0 mm — about 123.0 mm more. On width, the A3 Paper measures 297.0 mm against the A4 Paper's 210.0 mm — about 87.0 mm more. They match almost exactly in thickness, at 0.1 mm.