How accurate are the machines at the gym?

Not accurate. On a treadmill, anyways. What happens on a treadmill is that it calculates how many calories you should have lost for running at that speed, for that ammount of time, and for that weight. of course a variable is thrown in there such as the length of your legs. a person with longer legs won't have to push as hard on a treadmill because they cover more distance with each step as a shorter person may have to work harder to cover the same ammount of ground.  more