Standard Paper Sizes Guide: A4, A3, B5, Letter in cm & Inches

1. Overview of ISO 216 International Paper Standards

The ISO 216 standard governs paper sizes used across most countries globally. Designed based on the 1:√2 (approx 1:1.4142) aspect ratio, folding the paper in half maintains the exact same aspect ratio.

2. ISO A-Series Dimensions Reference Table

Format	Millimeters (mm)	Centimeters (cm)	Inches (in)
A0	841 × 1189 mm	84.1 × 118.9 cm	33.1 × 46.8 in
A1	594 × 841 mm	59.4 × 84.1 cm	23.4 × 33.1 in
A2	420 × 594 mm	42.0 × 59.4 cm	16.5 × 23.4 in
A3	297 × 420 mm	29.7 × 42.0 cm	11.7 × 16.5 in
A4 (Standard)	210 × 297 mm	21.0 × 29.7 cm	8.3 × 11.7 in
A5	148 × 210 mm	14.8 × 21.0 cm	5.8 × 8.3 in

3. North American Standards (ANSI / US Letter)

In the US, Canada, and Mexico, ANSI paper formats are standard instead of ISO sizes:

• US Letter: 8.5 × 11.0 in (215.9 × 279.4 mm / 21.59 × 27.94 cm)
• US Legal: 8.5 × 14.0 in (215.9 × 355.6 mm / 21.59 × 35.56 cm)

4. Screen Calibration Tip

Standard A4 paper (21.0 cm × 29.7 cm) works excellent as a physical calibration reference alongside credit cards when using online rulers.