Centimeters to Millimeters
Convert centimeter to millimeter instantly — type a value and read the result, with the exact formula shown.
Example
1 cm = 10 mm, 5 cm = 50 mm, 10 cm = 100 mm.
How it works
Millimeter = Centimeter × 10. Every value is converted through a single meter base unit using internationally defined conversion factors, so any from/to pair stays consistent.
Good to know
Converting centimeters to millimeters comes up constantly in everyday precision work: reading a tape measure or ruler, sizing parts for 3D printing and woodworking, sewing and pattern-making, eyeglass and screw measurements, and reporting medical or scientific measurements where a finer unit avoids decimals. Because a millimeter is one-tenth of a centimeter, switching to mm is simply a way to express the same length with whole numbers instead of fractions.
Both units are part of the metric (SI) system, which is built on powers of ten. The meter is the base unit; "centi-" means one-hundredth of a meter and "milli-" means one-thousandth. That shared decimal lineage is why the two units line up so cleanly, with no awkward conversion factor like the 2.54 you need when crossing into inches.
The rule of thumb is the easiest in all of unit conversion: just move the decimal point one place to the right, or multiply by 10. So 2.4 cm becomes 24 mm, and 0.75 cm becomes 7.5 mm. Going the other way, you move the decimal one place left (divide by 10), so 18 mm is 1.8 cm.
The most common mistake is multiplying or dividing by 100 instead of 10 — that confuses the cm-to-mm step with the cm-to-meter step. Another slip is dropping a trailing decimal: 5 cm is exactly 50 mm, not 5 mm. This conversion is exact, so there's no rounding error to worry about; any imprecision comes only from your original measurement.
Frequently asked questions
How do you convert centimeter to millimeter?
Multiply the number of centimeters by 10 to get millimeters. For example, 1 cm = 10 mm.
What is 1 centimeter in millimeters?
1 centimeter equals 10 millimeters (1 cm = 10 mm).
How many centimeters are in 1 millimeter?
There are 0.1 centimeters in 1 millimeter.
Is this converter free and private?
Yes. It runs entirely in your browser, so your inputs never leave your device, there is no sign-up, and it works offline once loaded.
Are the conversions exact?
Conversions use internationally defined factors and are exact where the definitions are exact (for example, 1 inch = 2.54 cm). Displayed results are rounded for readability.
People also ask
How many millimeters are in a centimeter?
There are exactly 10 millimeters in 1 centimeter, because a millimeter is one-tenth of a centimeter.
How do I convert cm to mm in my head?
Just move the decimal point one place to the right, which is the same as multiplying by 10. For example, 3.6 cm becomes 36 mm.
What is 15 cm in mm?
15 cm equals 150 mm (15 multiplied by 10).
What is 0.5 cm in millimeters?
0.5 cm equals 5 mm. Half a centimeter is five millimeters.
Which is bigger, a centimeter or a millimeter?
A centimeter is bigger. One centimeter equals 10 millimeters, so a millimeter is the smaller, finer unit.
How do I convert millimeters back to centimeters?
Divide the millimeters by 10, or move the decimal one place to the left. For example, 72 mm equals 7.2 cm.
Is the cm to mm conversion exact?
Yes, it is exact. Both are metric units defined as fixed fractions of a meter, so 1 cm is precisely 10 mm with no rounding involved.
How many mm is 2.5 cm?
2.5 cm equals 25 mm (2.5 multiplied by 10).
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