721 millimeters in kilometers

Conversion formula
How to convert 721 millimeters to kilometers?

We know (by definition) that: $1\mathrm{mm}=1e-06\mathrm{km}$

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

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

Conclusion: 721 ⁢ mm = 0.000721 ⁢ km

Conversion in the opposite direction

The inverse of the conversion factor is that 1 kilometer is equal to 1386.9625520111 times 721 millimeters.

It can also be expressed as: 721 millimeters is equal to $\frac{1}{\mathrm{1386.9625520111}}$ kilometers.

Approximation

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