How many miles should you walk in order to lose 20 pounds in one month?

Well if you walk 14 miles a week and eat 3500 less calorie in a week to you loss 2 pound a week so that's still only 8 lbs, you have to burn 3500 calorie for every pound of body fat, 2 mile walk would burn around 200 cals. So a lot of walking for 20 pounds.