How to convert inches to centimeters
Multiply the number of inches by 2.54. One inch is exactly 2.54 centimeters and 25.4 millimeters, a value fixed by the 1959 agreement between the US, the UK, Canada, Australia, New Zealand and South Africa that standardized the inch.
Worked example: a laptop has a 15.6 inch screen. 15.6 × 2.54 = 39.624 cm. A pipe with a 1 and 1/4 inch diameter, entered as 1.25, is 3.175 cm, or 31.75 mm.
Because 2.54 has two decimal places, the result of an inch measurement with up to two decimals has at most four, and the converter shows it without rounding.
Common sizes in inches and centimeters
- US Letter paper is 8.5 × 11 in, which is 21.59 × 27.94 cm. A4 is 21 × 29.7 cm, close to but not the same.
- TV sizes are the diagonal: 32 in is 81.3 cm, 43 in is 109.2 cm, 55 in is 139.7 cm, 65 in is 165.1 cm.
- A standard door is often 80 in high, which is 203.2 cm, and 36 in wide, which is 91.44 cm.
- Rulers and tapes mark 12 in as 30.48 cm, and 1 yard (36 in) as 91.44 cm.
- Phone screens are quoted by diagonal too: a 6.1 in display is 15.494 cm across the corner.
Screen sizes are measured corner to corner, so a 55 inch TV is much less than 55 inches wide. The wide and high sides depend on the shape of the panel.
Reading fractions on a tape measure
American tape measures divide the inch into halves, quarters, eighths and sixteenths. To enter a fraction, divide the top number by the bottom and add it to the whole number:
- 1/16 in = 0.0625 in = 1.5875 mm
- 1/8 in = 0.125 in = 3.175 mm
- 1/4 in = 0.25 in = 6.35 mm
- 1/2 in = 0.5 in = 12.7 mm
- 3/4 in = 0.75 in = 19.05 mm
For the other direction see cm to inches, and for larger distances feet to meters.