Treadmill - 15% incline @ 5 mph

This activity burns approximately 901 calories per hour

By the time many fitness enthusiasts reach a 5-mph walking pace, they're ready for a challenge. Try bringing your walking inside onto a treadmill! After a brief warm-up, start increasing the incline by 1 to 2% every 5 minutes until you reach a 15% grade. You'll find that you get a better workout in the same amount of time as walking on a level course.