Treadmills measure total calorie burn.
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Tracking the calories you burn can help you control your weight, whether you're looking to lose it, maintain it or even gain it. But your calorie estimate is only helpful if it's accurate. Estimates that include your basal metabolic rate -- the calories you burn at rest -- can give you a skewed view of your calorie burn. Understand how treadmills estimate your calorie burn and make adjustments as needed.
According to Alex Hutchinson, a runner and postdoctoral physicist, treadmills do take your basal metabolic rate into account when calculating your calorie burn. As Hutchison explains, a 176-pound woman walking at a speed of 2.4 mph will burn 240 calories according to a treadmill calculator. But the same woman would burn 80 calories on the couch, so her net calorie burn is actually only 160 calories. Hutchison notes that the difference between net and total calorie burn is more significant with lower-intensity exercise.
Adjusting Treadmill Numbers
Hutchison recommends subtracting one calorie per kilogram of body weight per hour of exercise to correct the treadmill's estimate. This will account for your basal metabolic rate. You can convert your weight from pounds to kilograms by dividing it by 2.2. A 200-pound person would weigh 91 kilograms, for example, and would subtract 91 calories from an hour on the treadmill -- or 1.5 calories per minute on the treadmill.
Other Treadmill Problems
Treadmill calorie calculators have other issues that affect their accuracy. The estimates are based on average people of the same weight as you. But if you have a greater fat percentage than the average person, you'll actually burn fewer calories than estimated because fat uses fewer calories than muscle. Conversely, if you have less-than-average aerobic fitness the treadmill will underestimate your calorie burn. Hutchison notes that treadmills also don't take into account cheats, like holding on to the handrails.
Net Calorie Formulas
According to Runner's World you can estimate your net calorie burn from running by multiplying your weight by 0.63 and multiplying the result by the number of miles that you run. For instance a 180-pound person would burn 340 net calories in a 3-mile run. To estimate the net calorie burn from walking, multiply your weight by 0.3 and then by the distance in miles. Based on this formula you will burn 162 calories walking 3 miles if you weigh 180 pounds.