# Basal Metabolism Calculator

To determine your metabolic rate, you must first calculate your basal metabolic rate (BMR). There are several different ways to determine the BMR. This calculator only makes an approximate calculation.

## Basal metabolism calculator

## More information about basal metabolism calculation

Basal metabolic rate (BMR) is the amount of energy needed at rest when the digestive system is inactive. It’s equivalent to calculating how much gas a car is consuming while parked. In such a case, the energy will only be used to protect vital organs including the heart, lungs, kidneys, nervous system, intestines, liver, lungs, genitals, muscles and skin.

For most people, over 70% of the total energy (calories) burned each day comes from maintenance. Physical activity accounts for about 20% of expenditure and ~10% is used for the digestion of food, also known as thermogenesis.

BMR is measured while awake under very restrictive conditions. An accurate BMR measurement requires a person’s sympathetic nervous system to be inactive, which means the person must be fully rested. Basal metabolism is often the largest component of a person’s total caloric needs. The daily calorie requirement is the BMR multiplied by a factor of 1.2 to 1.9, depending on the activity level.

In most cases, BMR is estimated by equations summarized from statistical data. The Harris-Benedict Equation was one of the earliest equations introduced. It was revised in 1984 to be more accurate and was used until 1990 when the Mifflin-St Jeor Equation was introduced. The Mifflin-St Jeor Equation has been shown to be more accurate than the Harris-Benedict Equation. The Katch-McArdle Formula is slightly different in that it calculates resting daily energy expenditure (RDEE) that takes lean body mass into account, something neither the Mifflin-St Jeor nor the Harris-Benedict Equation do. Of these equations, Mifflin-St Jeor Equation is considered the most accurate equation for calculating BMR except that the Katch-McArdle Formula may be more accurate for people who are thinner and know their body fat percentage. You can select the equation to use in the calculation by expanding the settings.

## Basal metabolism formulas

The three equations used by the calculator are listed below:

### Mifflin-St Jeor Equation

Male: BMR = (10 x weight, kg) + (6.25 x Height cm) – (5 x age + 5) Female: BMR = (10 x weight, kg) + (6.25 x Height cm) – (5 x age – 161)

### Harris-Benedict Equation

Male: BMR = 88,362 + (13,397 x weight, kg) + (4,799 x Height cm) – (5,677 x age) Female: BMR = 447,593 + (9,247 x weight, kg) + (3,098 x Height cm) – (4,330 x age)

### Katch-McArdle Equation

BMR = 370 + 21.6 x (1 – body fat ratio) x ağırlık, kg

## Factors affecting basal metabolism

**Muscle Mass**: Aerobic exercise such as running or cycling has no effect on BMR. However, anaerobic exercise such as weight lifting indirectly leads to a higher BMR because it builds muscle mass and increases resting energy expenditure. The more muscle mass an individual has in their physical composition, the higher the BMR needed to maintain their body at a certain level.

**Age**: The older and more flexible an individual is, the lower their BMR, or the lower the minimum caloric intake required to keep their organs functioning at a certain level.

**Genetics**: Inherited traits inherited from ancestors affect BMR.

**Weather**: Cold environments raise BMR due to the energy required to create homeostatic body temperature. Likewise, too much external heat can raise BMR, as the body expends energy to cool internal organs. BMR increases by about 7% for every 17 degrees Celsius increase in the body’s core temperature.

**Diet**: Small, routinely distributed meals increase BMR. On the other hand, fasting can reduce BMR by up to 30%. Similar to a phone that goes into power saving mode on the last 5% of its battery, a human body will make sacrifices such as energy levels, moods, maintenance of body physique and brain functions in order to use less calories more efficiently.

**Pregnancy**: Maintaining a separate fetus internally increases BMR. This is why pregnant women tend to eat more than usual. Also, menopause can increase or decrease BMR due to hormonal changes.

**Supplements**: Some supplements or medications raise BMR, mostly to accelerate weight loss. Caffeine is common.

## BMR Tests

Online BMR tests are not the most accurate method of determining an individual’s BMR. It is better to consult a certified specialist or measure BMR with a calorimeter device. These handheld devices are available at many health and fitness clubs, doctor’s offices, and weight loss clinics.

## Resting Metabolic Rate

While the two are used interchangeably, there is a fundamental difference in their definitions. The resting metabolic rate, or RMR for short, is the rate at which the body burns energy in a relaxed but not fully active state. It is also sometimes referred to as resting energy expenditure or REE. BMR measurements must satisfy total physiological balance, while RMR measurement conditions can be changed and defined by contextual limitations.

There are still poorly understood factors that determine BMR. Therefore, not all BMR calculations will be perfectly accurate in their measurements, even if the most precise methods are used through experts. Not all human body functions are yet fully understood, so calculations of total daily energy expenditure (TDEE) derived from BMR estimates are only estimates.