Millimeters to Centimeters (mm to cm)

How to convert millimeters to centimeters

Divide the millimeters by 10:

cm = mm ÷ 10

25 mm ÷ 10 = 2.5 cm. Dividing by 10 moves the decimal point one place to the left: 3 mm is 0.3 cm, 150 mm is 15 cm and 1,234 mm is 123.4 cm. The prefixes are exact: milli- is a thousandth and centi- a hundredth of a meter. The result also shows inches. To go the other way, use cm to mm.

Millimeters to centimeters chart

Where you see millimeters

Product listings from abroad give sizes in millimeters, while a ruler at home may be marked in centimeters with millimeter ticks: each small tick is 1 mm, each numbered line 1 cm.

Reading a metric ruler

Count whole centimeters at the numbered lines, then the small ticks after the last number: 4 cm and 7 ticks is 47 mm, or 4.7 cm. For drill bits, screws and jewelry, sizes stay in millimeters, so convert only when you need to compare with a measurement in centimeters or inches.

Rainfall and snow in millimeters

Weather services outside the U.S. report precipitation in millimeters, and 1 mm of rain means a layer of water 1 mm deep over flat ground — 1 liter on every square meter. A light shower is 1 to 2 mm, a wet day 10 to 20 mm (1 to 2 cm), and a tropical downpour can drop 50 mm in an hour. Snow is reported in centimeters because it is deeper: 10 cm of fresh snow usually melts to about 10 mm of water, a ten-to-one ratio that changes with how wet the snow is. To compare with a U.S. forecast in inches, divide millimeters by 25.4.

Millimeters and inches

A millimeter is 0.03937 inch, and an inch is exactly 25.4 mm. The result shows inches beside the centimeters. For inches as the main answer, see mm to inches; for meters, cm to meters.