Convert centimetres to millimetres

One centimetre is 10 millimetres. To convert any amount, multiply by 10. Going the other way, one millimetre is 0.1 centimetres.

Multiply the centimetre figure by 10. So mm = cm × 10. For a quick mental estimate, multiplying by about 10 gets you within a percent or so, which is close enough for most everyday purposes.

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.

One millimetre is roughly the thickness of a credit card, which is 0.76 mm. The millimetre is the working unit of engineering drawings and machining tolerances almost everywhere metric is used, because it avoids decimals for most part dimensions.

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 cm before converting introduces an error the conversion then multiplies.