Ans

Unit converter

Centimetres to inches.

Convert cm to in and in to cm. Type in either box and the other follows. Screen sizes, waist sizes and paper are all quoted differently either side of the Atlantic, and 2.54 is the only number you need.

cm → inExact definition
—
Centimetres to inches — common values, to 6 significant figures.
cmin
1 cm0.393701 in
2 cm0.787402 in
5 cm1.9685 in
10 cm3.93701 in
15 cm5.90551 in
20 cm7.87402 in
25 cm9.84252 in
30 cm11.811 in
40 cm15.748 in
50 cm19.685 in
75 cm29.5276 in
100 cm39.3701 in
1 cm=0.3937007874 in 1 in=2.54 cm

Definitions

  • The centimetre is a hundredth of a metre. It is the everyday metric unit for body and furniture measurements outside engineering.
  • The inch has been exactly 25.4 mm since the 1959 international yard and pound agreement. Screen and wheel sizes are still quoted in it.
  • This conversion is exact by definition. 1 cm = 0.3937007874 in.
  • 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 inches in a centimetre (0.393701), how many centimetres in an inch (2.54), and what 30 cm is in inches (11.811 in).

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