it various but you might check out lancaster.unl.edu/food/ftapr04-printfriend
best idea is to get pedometer that also counts cals burned
As a general guideline, a person will burn about 100 calories walking a mile. Expending just an additional 100 calories per day will help a person lose about 10 pounds a year. Or, allow a person to eat 100 more calories per day without gaining weight.