How do you find the cost of gas per mile

Take your MPG divided by the price of gas ... That's how you figure out the cost of a mile.

First, you'll want to take the number you wrote down in step 2 (the total distance of your trip) and divide it by the number you got from step 1 (your gas mileage). Next, multiply that figure by the number you wrote down in step 3 (the current price of gas), and then you're all done!