Running can relieve stress, improve your overall athletic performance, promote good health and, of course, burn calories to help you lose weight. Pinning down an average number of calories burned in 20 minutes of running really isn’t as simple as it seems. Your calorie burn depends on the intensity of your run — which translates into how many miles you cover, as well as the terrain — along with your size and age.

A General Rule: 100 Calories per Mile
A very rough rule of thumb is that, if you have an average healthy body weight, you’ll burn roughly 100 calories for every mile you cover. So, if you cover 1 1/2 miles in 20 minutes, you’ll burn about 150 calories. If you’re a faster runner and cover 3 miles, you’ll burn roughly 300 calories in the same amount of time. Of course, if you weigh more than average, you’ll burn more. If you weigh less, you’ll burn less.