21 millimeters in centimeters

Result

The conversion result is: 21 millimeters is equivalent to 2.1 centimeters.^[1]

Conversion formula
How to convert 21 millimeters to centimeters?

We know (by definition) that: 1 mm = 0.1 cm.

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

1 mm / 21 mm = 0.1 cm / x cm

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

x cm = (21 mm / 1 mm) * 0.1 cm → x cm = 2.1 cm

Conclusion:

21 mm = 2.1 cm

Conversion in the opposite direction

The inverse of the conversion factor is that 1 centimeter is equal to 0.476190476190476 times 21 millimeters.

It can also be expressed as: 21 millimeters is equal to 1 / 0.476190476190476 centimeters.

Approximation

An approximate numerical result would be: twenty-one millimeters is about zero centimeters, or alternatively, a centimeter is about zero point four eight times twenty-one millimeters.