21 centimeters in millimeters

Result

The conversion result is: 21 centimeters is equivalent to 210 millimeters.[1]

Conversion formula
How to convert 21 centimeters to millimeters?

We know (by definition) that: 1 cm = 10 mm.

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

1 cm / 21 cm = 10 mm / x mm

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

x mm = (21 cm / 1 cm) * 10 mm → x mm = 210 mm

Conclusion:

21 cm = 210 mm

Conversion in the opposite direction

The inverse of the conversion factor is that 1 millimeter is equal to 0.00476190476190476 times 21 centimeters.

It can also be expressed as: 21 centimeters is equal to 1 / 0.00476190476190476 millimeters.

Approximation

An approximate numerical result would be: twenty-one centimeters is about two hundred and ten millimeters, or alternatively, a millimeter is about zero times twenty-one centimeters.

Footnotes

[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).

Results may contain small errors due to the use of floating point arithmetic.