21 millimeters in kilometers

Result

The conversion result is: 21 millimeters is equivalent to 2.1e-05 kilometers.^[1]

Conversion formula
How to convert 21 millimeters to kilometers?

We know (by definition) that: 1 mm = 1e-06 km.

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

1 mm / 21 mm = 1e-06 km / x km

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

x km = (21 mm / 1 mm) * 1e-06 km → x km = 2.1e-05 km

Conclusion:

21 mm = 2.1e-05 km

Conversion in the opposite direction

The inverse of the conversion factor is that 1 kilometer is equal to 47619.0476190476 times 21 millimeters.

It can also be expressed as: 21 millimeters is equal to 1 / 47619.0476190476 kilometers.

Approximation

An approximate numerical result would be: twenty-one millimeters is about zero kilometers, or alternatively, a kilometer is about forty-seven thousand, six hundred and nineteen point zero five times twenty-one millimeters.