Convert inches to centimetres

One inch is 2.54 centimetres. To convert any amount, multiply by 2.54. Going the other way, one centimetre is 0.393700787 inches.

Multiply the inch figure by 2.54. So cm = in × 2.54. For a quick mental estimate, multiplying by about 2.54 gets you within a percent or so, which is close enough for most everyday purposes.

One inch is roughly the width of an adult thumb. The inch has been exactly 25.4 millimetres since 1959. Screen sizes, pipe diameters and tyre rims are still specified in inches almost universally.

One centimetre is about the width of an adult fingernail. The centimetre is the everyday metric unit for body measurements and paper sizes, though it is not an SI-preferred prefix step — engineers tend to jump from millimetres to metres.

Yes. Since the 1959 international yard and pound agreement, the imperial and metric systems are related by exact definitions rather than measurements — the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg. Everything derived from those, including this conversion, is therefore exact. Round at the end rather than partway through, since rounding in before converting introduces an error the conversion then multiplies.