Ans

Unit converter

Millimetres to centimetres.

Convert mm to cm and cm to mm. Type in either box and the other follows. A tenth, no more than that — but it is the conversion a drawing dimensioned in millimetres needs when the spec sheet is in centimetres.

mm → cmExact definition
—
Millimetres to centimetres — common values, to 6 significant figures.
mmcm
1 mm0.1 cm
5 mm0.5 cm
10 mm1 cm
25 mm2.5 cm
50 mm5 cm
100 mm10 cm
250 mm25 cm
500 mm50 cm
1000 mm100 cm
1 mm=0.1 cm 1 cm=10 mm

Definitions

  • The millimetre is a thousandth of a metre, and the unit most engineering drawings in the UK are dimensioned in.
  • The centimetre is a hundredth of a metre. It is the everyday metric unit for body and furniture measurements outside engineering.
  • This conversion is exact by definition. 1 mm = 0.1 cm.
  • The metre is SI; every imperial and US customary length here is defined exactly in terms of it by the 1959 international yard and pound agreement.

How it works

One direction multiplies and the other divides by the same number, so nothing is lost by going back and forth.

The value passes through m, the unit every other length & distance unit on the site is defined against, rather than a number written into this page on its own. That is why the figure here, the figure in the table above and the general length & distance converter always agree.

Display precision limits significant figures rather than decimal places, because one fixed number of decimals is useless across a range this wide. Very large and very small results switch to scientific notation with a proper superscript exponent. The editable box always holds a plain number at full working precision, so you can carry on from either side.

Common questions this answers: how many centimetres in a millimetre (0.1), how many millimetres in a centimetre (10), and what 25 mm is in centimetres (2.5 cm).

From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.