This Calorie Calculator is based on several equations, and the results of the calculator are based on an estimated average. The Harris-Benedict Equation was one of the earliest equations used to calculate basal metabolic rate (BMR), which is the amount of energy expended per day at rest. It was revised in 1984 to be more accurate and was used up until 1990, when the Mifflin-St Jeor Equation was introduced. The Mifflin-St Jeor Equation also calculates BMR, and has been shown to be more accurate than the revised Harris-Benedict Equation. The Katch-McArdle Formula is slightly different in that it calculates resting daily energy expenditure (RDEE), which takes lean body mass into account, something that neither the Mifflin-St Jeor nor the Harris-Benedict Equation do. Of these equations, the Mifflin-St Jeor Equation is considered the most accurate equation for calculating BMR with the exception that the Katch-McArdle Formula can be more accurate for people who are leaner and know their body fat percentage. The three equations used by the calculator are listed below:

For men:BMR = 13.397W + 4.799H - 5.677A + 88.3602
For women:BMR = 9.247W + 3.098H - 4.330A + 447.593


where:
W is body weight in kg
H is body height in cm
A is age
F is body fat in percentage

Activity Factor

The value obtained from these equations is the estimated number of calories a person can consume in a day to maintain their body-weight, assuming they remain at rest. This value is multiplied by an activity factor (generally 1.2-1.95), dependent on a person's typical levels of exercise, in order to obtain a more realistic value for maintaining body-weight (since people are less likely to be at rest throughout the course of an entire day). 1 pound, or approximately 0.45 kg, equates to about 3,500 calories. As such, in order to lose 1 pound per week, it is recommended that 500 calories be shaved off the estimate of calories necessary for weight maintenance per day. For example, if a person has an estimated allotment of 2,500 calories per day to maintain body-weight, consuming 2,000 calories per day for one week would theoretically result in 3,500 calories (or 1 pound) lost during the period.It is important to remember that proper diet and exercise is largely accepted as the best way to lose weight. It is inadvisable to lower calorie intake by more than 1,000 calories per day, as losing more than 2 pounds per week can be unhealthy, and can result in the opposite effect in the near future by reducing metabolism. Losing more than 2 pounds a week will likely involve muscle loss, which in turn lowers BMR, since more muscle mass results in higher BMR. Excessive weight loss can also be due to dehydration, which is unhealthy. Furthermore, particularly when exercising in conjunction with dieting, maintaining a good diet is important, since the body needs to be able to support its metabolic processes and replenish itself. Depriving the body of the nutrients it requires as part of heavily unhealthy diets can have serious detrimental effects, and weight lost in this manner has been shown in some studies to be unsustainable, since the weight is often regained in the form of fat (putting the participant in a worse state than when beginning the diet). As such, in addition to monitoring calorie intake, it is important to maintain levels of fiber intake as well as other nutritional necessities to balance the needs of the body.

Ideal Weight

D. R. Miller Formula (1983)
Male:56.2 kg + 1.41 kg per inch over 5 feet
Female:53.1 kg + 1.36 kg per inch over 5 feet


Age

In theory, age shouldn't be a large determinant of a IBW past the ages of 14-15 for girls and 16-17 for boys, after which most people stop growing. It is actually expected that human males and females to lose 1.5 and 2 inches in height respectively by age 70. It is important to remember that as people age, lean muscle mass decreases and it is easier to accumulate excess body fat. This is a natural process, though it is possible to lessen the effects of aging by adopting various habits such as monitoring diet, exercise, stress, and sleep.