645 decimeters in kilometers
Result
The conversion result is: 645 decimeters is equivalent to 0.0645 kilometers.[1]
Conversion formula
How to convert 645 decimeters to kilometers?
We know (by definition) that: 1 dm = 0.0001 km.
We can set up a proportion to solve for the number of kilometers.
1 dm / 645 dm = 0.0001 km / x km
Now, we cross multiply to solve for our unknown x:
x km = (645 dm / 1 dm) * 0.0001 km → x km = 0.0645 km
Conclusion:
645 dm = 0.0645 km

Conversion in the opposite direction
The inverse of the conversion factor is that 1 kilometer is equal to 15.5038759689922 times 645 decimeters.
It can also be expressed as: 645 decimeters is equal to 1 / 15.5038759689922 kilometers.
Approximation
An approximate numerical result would be: six hundred and forty-five decimeters is about zero point zero six kilometers, or alternatively, a kilometer is about fifteen point five zero times six hundred and forty-five decimeters.
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.