# How can you convert centimeters to millimeters?

##### 1 Answer

**Quick Answer: Multiply by 10.**

To do any conversion, you find the relationship between the two units.

In this case,

Therefore

This gives you two conversion factors:

and if you look at the equation, you'll see that

**EXAMPLE**

Convert 3.1 cm into millimetres.

You multiply by a conversion factor:

Choose the one that gives you the correct units for the answer.

Note that the "cm" cancels out and leaves you with the answer in “mm”. If you had chosen the other conversion factor, you would have gotten

The strange units for the answer tell you that you have made a mistake.

**LAST RESORT**

If you can’t remember that

Then you can convert “cm” to “m” and “m” to “mm”.

It's an extra step, but it always works.