Okay, so first you divide 80 in half, then you time yourself to see how long it takes you to run a mile. After that you decide if you are in shape, out of shape, or just sloppy fat. Then you take a measurement of your wheel to see how many times it turns in a mile. Next weigh a truck, then check your air pressure....Owwww brain cramp, wait you're confused? Why? I make perfect sense.