Figure out how many miles you have initially. For example, let's say that you are trying to convert 10 miles to kilometers.
Multiply the number of miles you have by the correct conversion factor. In this case, the conversion factor is 1.61. This is because 1 mile = 1.609344 kilometers. So for this example, you would multiply 10 miles by 1.61.
The result that you get is the number of kilometers that you have. So, 10*1.61 = 16.1 kilometers.