640 millimeters in centimeters

Conversion formula
How to convert 640 millimeters to centimeters?

We know (by definition) that: $1\mathrm{mm}=0.1\mathrm{cm}$

We can set up a proportion to solve for the number of centimeters.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 640 ⁢ mm = 64.0 ⁢ cm

Conversion in the opposite direction

The inverse of the conversion factor is that 1 centimeter is equal to 0.015625 times 640 millimeters.

It can also be expressed as: 640 millimeters is equal to $\frac{1}{\mathrm{0.015625}}$ centimeters.

Approximation

An approximate numerical result would be: six hundred and forty millimeters is about zero centimeters, or alternatively, a centimeter is about zero point zero two times six hundred and forty millimeters.