The Dietary Reference Intakes, or DRI, have made calculating an estimate of your calories burned and physical activity level possible for the general public. Researchers assigned a numerical value to varying degrees of physical activity. This allows you to easily estimate of how many calories your body burns performing basic metabolic functions and how many calories you burn when adding physical activity to your routine.
Basal Energy Expenditure
To begin figuring out how many calories you burn each day, you must first know how many calories your body will burn without effort from you. This is known as your basal energy expenditure, or BEE. Simply defined, it is the calories your body uses to perform biological functions like breathing and digesting.
The formula for women:
293 - (3.8 x age in years) + (456.4 x height in meters) + (10.12 x weight in kilograms)
The formula for men:
247 - (2.67 x age in years) + 401.5 x (height in meters) + (8.6 x weight in kilograms)
Quantifying Your Physical Activity
Next, you must determine your physical activity level. Scientists have done the hard part, now all you have to do is be completely honest. There are four "degrees" of activity levels. Choose the one that best describes your lifestyle, then select the corresponding physical activity factor based on your gender.
Sedentary: your activity level is limited to the activities required for independent daily living. Men and women's activity factor: 1.0
Low Active: Your activity level includes the activities required for independent daily living and the equivalent of 30 minutes of walking at 4 miles per hour daily. The factor for men is 1.12; For women, 1.14.
Active: your activity level includes the activities required for independent daily living and the equivalent of 60 minutes of walking at 4 miles per hour daily. The factor for men is 1.27; for women, 1.27.
Very Active: Your activity level includes the activities required for independent daily living and the equivalent of 4 hours of walking at 4 miles per hour daily. The factor for men is 1.54; for women,: 1.45.
Total Energy Expenditure
Finally, you can determine how many calories you burn each day using the total energy expenditure formula. This formula takes into account your physical activity level, gender, height, weight and age.
The formula for women:
387 - (7.31 x age in years) + Physical Activity factor x [(10.9 x weight in kg) + (660.7 x height in meters)]
The formula for men:
864 - (9.72 x age in years) + Physical Activity factor x [(14.2 x weight in kg) + (503 x height in meters)]
Reaching Your Goals
Although there are more in-depth methods to do these computations, such as using metabolic breath tests, testing the thermogenic effect of your food intake and ranking metabolic equivalents to your activities, this is a simple method you can use at home to evaluate your efforts and help you reach your goals.
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