# cm to mm Converter

Created by Davide Borchia
Reviewed by Komal Rafay
Last updated: May 04, 2023

Converting cm to mm is an easy and fundamental conversion of length measurement units that interest our daily lives: centimeters and millimeters are the units that measure the scale of objects we can handle with ease. While we efficiently assess a measure in centimeters, it may be harder to do so using millimeters. Keep reading our tool if you want to learn:

• Some facts about centimeters and millimeters;
• The conversion from cm to mm;
• Examples of conversion from centimeter to millimeter using real-life examples;

and much more!

## Centimeters and millimeters

Centimeters and millimeters are metric measurement units for length, corresponding to two submultiples of the metric base unit for length: the meter. The conversions between these units and the meter are:

$1\ \rm mm = 1\cdot 10^{-3}\ \rm m$

For the millimeter, and:

$1\ \rm cm = 1\cdot 10^{-2}\ \rm m$

For the centimeter. Notice how the centimeter uses exponent $-2$. In a scientific context, while still acceptable, using the centimeter is not advisable: the preferred subunits come with multiples of $3$ as exponents.

#### Calculate the cm to mm conversion

To convert from centimeters to millimeters, we need to combine the exponents we've seen above. To do so, we calculate the ratio that would allow us to find a measure in millimeters starting from one in centimeters. This ratio will have centimeters at the denominator and millimeters at the numerator:

$\frac{1,\!000\ \rm{mm/m}}{100\ \rm cm/m}=10\ \rm mm/cm$

The formula above tells us that each centimeter corresponds to ten millimeters. This will be enough to find the conversion between the two units.

## The conversion from cm to mm

As we said above, a centimeter corresponds to ten millimeters. In mathematical terms, we write:

$1\ \rm cm = 10\ \rm mm$

To convert from cm to mm, we then have to multiply the measure in centimeters by 10: the conversion corresponds to a ten-fold increase in the magnitude of the measure.

To perform the inverse conversion, divide a measure in millimeters by $10$ to find the corresponding measure in centimeters.

## Convert centimeter to millimeter: worked examples

How many millimeters is a 1.5 cm pipe? Remember how many millimeters are in a centimeter to find the answer: the answer is ten. Since converting from centimeters to millimeters must correspond to an increase in the absolute value of the measure, multiply the measure by $10$:

$\begin{split} 1.5\ \rm cm &\equiv 1.5 \ \rm cm \cdot 10\ \rm mm/cm \\ &= 15\ \rm mm \end{split}$

The inverse conversion may be slightly more bothering as it involves a division. It's an easy division, however! To how many centimeters does a $9\ \rm mm$ length correspond? Divide the measure by $10$ to find the answer.

$\begin{split} 9\ {\rm mm} &\equiv \frac{9 \ {\rm mm}}{10\ {\rm mm/cm}} \\ &= 0.9\ {\rm cm} \end{split}$

## FAQ

### How do I convert from centimeter to millimeter?

To convert from centimeters to millimeters, follow these easy steps:

1. Find your measurements in centimeters. The easiest way to do so is to use a ruler or tape.
2. Convert cm to mm by multiplying the measure by 10.
3. The result is your measure expressed in mm.

### How do I calculate cm and mm for a length of one inch?

One inch corresponds to 2.54 cm. To find how many millimeters this length corresponds, use the conversion factor from cm to mm:
1 cm = 10 mm.
Hence, starting from a length of 2.54 cm, we find:
2.54 cm = 2.54 cm x 10 mm/cm = 25.4 mm
As you can see, an inch is much closer to a centimeter than a millimeter.

### What is the conversion from millimeter to centimeter?

The conversion from millimeters to centimeters is the opposite of the conversion from cm to mm. To find this conversion, follow these steps:

1. Find how many millimeters are in a meter: 1 m = 1000 m.
2. Find how many centimeters are in a meter: 1 m = 100 cm.
3. Find the conversion factor from mm to cm using the ratio between the conversions we found above: 1 mm = 1 mm × 100 cm/1000 mm = 0.1 cm

To convert from mm to cm, we then need to divide by 10.

Davide Borchia
cm
mm
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