CM to MM Converter

Multiply the centimeters by 10, because 1 cm is 10 mm. The decimal point moves one place to the right: 3.7 cm is 37 mm, 12 cm is 120 mm and 0.5 cm is 5 mm. In the converter, choose "cm → mm" and enter the length.

25 mm is 2.5 cm. Divide the millimeters by 10, which moves the decimal point one place to the left. In the same way 50 mm is 5 cm, 6 mm is 0.6 cm and 100 mm is 10 cm.

30 cm equal 300 mm, because 30 × 10 = 300. That is also 0.3 m. A common 12 inch ruler is about 30.5 cm long, which is 304.8 mm.

3500 mm is 350 cm, since 3500 / 10 = 350. In meters that is 3.5 m. Dividing by 10 is a handy check for a long measurement that a spec sheet gives in millimeters.

100 cm are 1,000 mm. That is exactly 1 meter, because a meter is 100 centimeters or 1,000 millimeters. Multiply by 10 again for 200 cm = 2,000 mm.

86.36 cm is 863.6 mm: 86.36 × 10 = 863.6. As a US customary length that is 34 inches, since 34 × 2.54 = 86.36 cm. The converter shows the same length in meters too, 0.8636 m.

The symbol is cm, in lowercase and without a period. The same symbol is used for one centimeter and for many, so write 1 cm and 5 cm. A millimeter is mm. The US customary abbreviation for the inch is in, and 1 in is exactly 2.54 cm.

Turn both lengths into the same unit before you add them. For 7 cm plus 4 mm, change 7 cm to 70 mm and add 4 mm to get 74 mm, which is 7.4 cm. Or change the 4 mm to 0.4 cm and add 7 cm.

7.6 cm is 76 mm, and adding 4mm gives 80 mm. In centimeters the sum is 7.6 + 0.4 = 8.0 cm, or 0.08 m. Always convert before you add, because 7.6 + 4 = 11.6 mixes two different units.

One inch is exactly 25.4 mm, which is 2.54 cm. So 2.54 cm are 25.4 mm, 6.35 cm are 63.5 mm (2.5 inches) and 50 mm are about 1.97 inches. The inch has been defined this way since 1959, in the United States and elsewhere.

Move the decimal point one place. For cm to mm it moves right (5.8 cm becomes 58 mm), and for mm to cm it moves left (58 mm becomes 5.8 cm). Add a zero when you run out of digits: 7 mm is 0.7 cm.

Millimeters avoid decimals for small parts. A metric drill bit of 6.5 mm is easier to read than 0.65 cm, and tolerances on machine parts are given in tenths or hundredths of a millimeter. In metric countries and metric specs, lengths of people and furniture, which are larger, are usually given in centimeters. US labels for these mostly use inches.