Paper formats
A3 vs A4: compare page dimensions
See the relationship between two familiar A-series formats.
By Printer Paper Size Team•
A3 measures 297 × 420 mm; A4 measures 210 × 297 mm. The long side of A4 equals the short side of A3.
A useful layout relationship
Two A4 pages can sit side by side across an A3 sheet in landscape orientation. That does not automatically leave room for printer margins, crop marks or bleed. A production layout may need a larger sheet.
For a simple enlargement from A4 to A3, the linear scale is approximately 141.4%, not 200%. Doubling both side lengths would produce four times the area.