Mayo Clinic states the number of calories a person burns in a day varies based on her basal metabolic rate and that person's individual level of physical activity. The BMR is the number of calories the body utilizes to perform basic human functions such as breathing.
Mayo Clinic goes on to explain that a person's BMR varies based on factors such as age, gender, body composition and size. Global RPh provides both the equation to discover a BMR and the equation to take the level of physical activity into account.
For men, BMR = (9.99 x weight in kg) + (6.25 x height in cm) - (4.92 x age) + 5
For women, BMR = (9.99 x weight in kg) + (6.25 x height in cm) - (4.92 x age) - 161.
To calculate daily caloric needs, the BMR is multiplied by the activity factor.
Sedentary individuals = BMR x 1.2
Mildly active individuals = BMR x 1.3 - 1.375
Moderately active individuals = BMR x 1.5 - 1.55
Heavily active or labor intensive individuals = BMR x 1.7
For extremely active individuals = BMR x 1.9
These values determine the daily caloric needs based on the individual at the time of calculation and need to be adjusted as factors such as weight, age and activity level change.