A standard sheet of paper has different sizes depending on the region. The most widely used international standard for paper sizes is the A series, defined by the ISO 216 standard. The most common size in this series is A4, which measures 8.27 × 11.7 inches or 210 × 297 mm
. In North America, the most popular formats are Letter (8.5 × 11 inches), Legal (8.5 × 14 inches), and Tabloid (11 × 17 inches)
. The A series uses an aspect ratio of 1:√2, and other sizes in the series are defined by folding the paper in half, parallel to its smaller sides
