Centimeters to Millimeters Converter
Enter a length in centimeters and read it in millimeters right away. One centimeter equals ten millimeters, so the converter simply multiplies your number by 10.
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Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
How many millimeters are in a centimeter?
A centimeter is made of 10 millimeters. Both units are fractions of the meter: centi- is one hundredth and milli- is one thousandth, so a millimeter is a tenth of a centimeter.
millimeters = centimeters × 10To convert back, divide millimeters by 10.
On a metric ruler this is easy to see. The numbered marks are centimeters and the nine short ticks between two numbers split each centimeter into ten millimeters.
When millimeters are preferred
Technical drawings, machine parts, screws, camera lenses and phone thicknesses are specified in millimeters because the unit gives whole numbers for small sizes. Paper is a typical bridge between the two: an A4 sheet is 21.0 cm by 29.7 cm in centimeters and 210 mm by 297 mm in millimeters.
How to convert cm to mm
- Put the length in centimeters in the first field.
- The second field shows the length in millimeters.
- Move the decimal point one place to the right if you want to check it by hand.
Example 1. A screw 3.7 cm long is 3.7 × 10 = 37 mm long.
Example 2. A 0.45 cm thick glass pane is 4.5 mm thick.
Example 3. A 12.5 cm cable is 125 mm long.
For areas multiply by 100, not 10, because 1 cm² = 10 mm × 10 mm = 100 mm². A 2 cm by 3 cm label has an area of 6 cm², which is 600 mm². Check: 20 mm × 30 mm = 600 mm².
Mixed lengths and paper sizes
A length written as 14 cm 7 mm is 14.7 cm, and therefore 147 mm. Convert the whole centimeters to millimeters (14 × 10 = 140) and add the loose millimeters (140 + 7 = 147).
ISO paper formats are a good practice set, since they are quoted in both units:
| Format | Centimeters (cm) | Millimeters (mm) |
|---|---|---|
| A3 | 29.7 × 42 | 297 × 420 |
| A4 | 21 × 29.7 | 210 × 297 |
| A5 | 14.8 × 21 | 148 × 210 |
| A6 | 10.5 × 14.8 | 105 × 148 |
Centimeters to millimeters table
| Centimeters (cm) | Millimeters (mm) |
|---|---|
| 0.1 | 1 |
| 0.5 | 5 |
| 1 | 10 |
| 2 | 20 |
| 2.5 | 25 |
| 5 | 50 |
| 7.5 | 75 |
| 10 | 100 |
| 15 | 150 |
| 25 | 250 |
| 50 | 500 |
| 100 | 1,000 |
| 250 | 2,500 |
| 1,000 | 10,000 |
Notes on the result
Multiplying by 10 never loses information, but the display is rounded to four decimals, which only matters for inputs with more than five decimal places. Trailing zeros are removed, so 25 cm shows as 250.
For the opposite direction use the millimeters to centimeters converter. Other lengths in this family are covered by the centimeters to decimeters, centimeters to meters, centimeters to inches and centimeters to feet converters.
Frequently asked questions
How do you convert centimeters to millimeters?
Multiply the number of centimeters by 10. For example, 6.4 cm × 10 = 64 mm.
How many millimeters are in 1 cm?
There are 10 millimeters in 1 centimeter.
Is a millimeter smaller than a centimeter?
Yes, a millimeter is one tenth of a centimeter, so a length has ten times as many millimeters as centimeters.
How do I convert cm² to mm²?
Multiply by 100. A square centimeter is 10 mm by 10 mm, which is 100 square millimeters.
References
Cite this converter and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). Centimeters to Millimeters Converter. Reeliy. https://reeliy.com/converters/convert-cm-to-mm-centimeters-to-millimeters“Centimeters to Millimeters Converter.” Reeliy, 2026, https://reeliy.com/converters/convert-cm-to-mm-centimeters-to-millimeters.