Converting Miles per Hour to Minutes per Mile
If you use a treadmill as part of your marathon training, you may need a formula to convert miles per hour to minutes per mile. Follow these steps to see how:

Divide 60 by whatever miles per hour the treadmill displays.
For example, if the treadmill says you’re running 7.1 miles per hour, divide 60 by 7.1, and you get 8.45 (almost 9 minutes).

Subtract the minutes so that you’re left with just the decimal that represents the number of seconds, and then multiply that decimal amount by 60.
Subtract 8 and multiply .45 by 60 to get 27.

Add that number back to the minutes, and you have your pace.
8 minutes + 27 seconds = 8:27 minutes per mile.