Inches and centimetres converter

The inch is an old English unit of length that is still used for screens, wheels, pipes and jeans. Since 1959 it has been defined exactly: one inch is 2.54 centimetres. Its symbol is in, or a double prime: 55″.

The size of a TV is given in inches as the length of its diagonal, the distance from one corner of the screen to the opposite corner, not its width. A 55-inch TV is about 122 cm wide, but its diagonal is nearly 140 cm. How the width, height and diagonal are related is shown in the rectangle diagonal calculator.

From inches to centimetres

From centimetres to inches

How it works

The calculator converts using these formulas:

$$1\text{inch}=2.54\text{cm},\text{cm}=\text{inches}\cdot 2.54,\text{inches}=\frac{\text{cm}}{2.54}$$

To convert a 55″ TV diagonal, multiply by 2.54:

$$55\cdot 2.54=139.7\text{cm}$$

The other way round, a 30 cm ruler is

$$\frac{30}{2.54}\approx 11.81\text{inches}$$

long, just under a foot. A foot is 12 inches, or 30.48 cm.