Determining how many calories you burn while walking or running on a treadmill is not always easy. Most treadmill displays show an estimate of calories burned, but may be inaccurate. Older or budget treadmills may not calculate calories for you at all.
Fortunately, the American College of Sports Medicine has several equations that can help you determine your caloric expenditure on a treadmill.
Know your speed, grade, weight and time spent exercising. Record this information on a piece of scratch paper. As an example, consider a person going 2.5 mph at a 2 percent incline for 30 minutes at a weight of 130 pounds.
Convert the units for use in the equation. Change mph to meters per minute by multiplying mph by 26.8. In the above example: 2.5 mph x 26.8 = 67 meters per minute.
Write percent grade as a decimal. For the example: 2 percent / 100 = .02.
Convert your body weight into kilograms by dividing your weight in pounds by 2.2; for example, 130 lbs. / 2.2 = 59.09 kg.
Complete the equation. If your speed was 3.7 mph or less, use the walking formula: (0.1 x speed) + (1.8 x speed x grade) + 3.5. If your speed was faster than 3.7 mph, use the running equation: (0.2 x speed) + 0.9 x speed x grade) + 3.5.
Insert your speed and grade from Step 2 into the correct formula.
For the example: (0.1 x 67 meters per minute) + (1.8 x 67 meters per minute x 0.02 grade) + 3.5].
Calculate the results. Use your calculator to find how much oxygen you used. Multiply the numbers in parentheses first and then add those two answers with 3.5.
In the example: (6.7) + (2.4) + 3.5 = 12.6 mL/kg/min.
Calculate calories per minute. Multiply your oxygen used in Step 4 by your weight in kilograms.
For this example: 12.6 mL/kg//min x 59.09 kg = 744.534 mL/min.
Dividing this number by 200 gives you your caloric expenditure per minute.
For the example: 744.53 / 200 = 3.72 calories per minute.
The sample 130-pound person thus burned 3.72 calories per minute
Calculate total calories used. Multiply your calories per minute by your minutes of exercise to find your total caloric expenditure.
Example: 3.72 calories per minute x 30 minutes = 111.6 calories.