A4 is slightly narrower and a bit longer than North American Letter size paper.

ISO A Sizes

A0:
841 mm x 1,189 mm
(33.11 in. x 46.81 in.)
A1:
594 mm x 841 mm
(23.39 in. x 33.11 in.)
A2:
420 mm x 594 mm
(16.54 in. x 23.39 in.)
A3:
297 mm x 420 mm
(11.69 in. x 16.54 in.)
A4:
210 mm x 297 mm
(8.27 in. x 11.69 in.)
A5:
148 mm x 210 mm
(5.83 in. x 8.27 in.)
A6:
105 mm x 148 mm
(4.13 in. x 5.83 in.)
A7:
74 mm x 105 mm
(2.91 in. x 4.13 in.)