Paper Size Converter
Convert between A-series paper sizes, US Letter, Legal and Tabloid with dimensions in mm, cm and inches
Paper Size
A4
Aspect Ratio: 0.71:1
Dimensions
Millimeters
210.0 x 297.0 mm
Centimeters
21.00 x 29.70 cm
Inches
8.27" x 11.69"
Pixels (150 DPI)
1240 x 1754px
Pixels (300 DPI)
2480 x 3508px
A-series paper is defined by ISO 216. A4 is the most common size worldwide. 150 DPI is suitable for screen, 300 DPI for print.
International Paper Sizes
Two main systems: ISO 216 (used globally outside North America) - A0, A1, A2, A3, A4, A5, etc. with each size being half of the previous. American/Canadian uses Letter (8.5 × 11 in), Legal (8.5 × 14 in), Tabloid (11 × 17 in), etc. - sizes have no direct ratio relationship.
Common conversions: A4 (210 × 297 mm) ≈ Letter (216 × 279 mm) - very close, but A4 is slightly narrower and taller. A3 ≈ Tabloid. A5 ≈ Half-Letter. The square-root-of-2 ratio in ISO sizes means folding any A-size in half gives the next smaller size with the same proportions.
Common Paper Sizes
| ISO | Size (mm) | Size (in) | US Equivalent |
|---|---|---|---|
| A0 | 841 × 1189 | 33.1 × 46.8 | n/a |
| A1 | 594 × 841 | 23.4 × 33.1 | n/a |
| A2 | 420 × 594 | 16.5 × 23.4 | Tabloid Extra |
| A3 | 297 × 420 | 11.7 × 16.5 | Tabloid |
| A4 | 210 × 297 | 8.3 × 11.7 | Letter |
| A5 | 148 × 210 | 5.8 × 8.3 | Half Letter |
| A6 | 105 × 148 | 4.1 × 5.8 | Index card |
| A7 | 74 × 105 | 2.9 × 4.1 | Postcard |
Frequently Asked Questions
Why doesn't the US use A4?
Historical accident. The Lincoln-era US standardised on 8.5 × 11 inch paper before ISO sizes were established (1922). Switching cost would be substantial - all forms, file folders, printers, copiers built for Letter. Hardware in the US still optimised for 8.5 × 11.
Are A4 and Letter the same?
Close but not identical. A4: 210 × 297 mm. Letter: 216 × 279 mm. A4 is slightly narrower (6 mm) and taller (18 mm). Most printers handle both; Excel/Word default page setup defaults to A4 or Letter based on locale.