Basal Metabolic Rate Calculator

What is BMR? 

Basal metabolic rate, or BMR, is the amount of energy your body needs to perform basic functions such as respiration, cardiac function, homeostasis, and so on.

BMR is determined by gender, age, and body weight. 60-70% of daily energy expenditure comes from basal metabolism.

When you’re trying to lose weight, many people focus on the number on the scale. But that’s not the best way to measure your progress—your basal metabolic rate (BMR) is a much better indicator.

What is BMR Calculator?

The Basal Metabolic Rate calculator is a simple tool used to estimate the basal metabolic rate of your body and measure the kilocalories required to sustain life processes at rest—essentially, what your body needs to keep you healthy. 

Because BMR measures the rate at which one’s body burns calories when a person is resting, it can only be accurately calculated after fasting for 12 hours and getting a whole night’s sleep—with no physical activity or emotional excitement. 

Why is BMR Calculator important?

Because it gives you an idea of how many calories you burn every day at rest—understanding your BMR allows you to set realistic fitness goals, including losing weight or gaining muscle mass. If you know how many calories your body needs each day, you can use the information to ensure the foods and drinks you consume provide enough energy without causing a caloric surplus or deficiency. This is how you can utilise the BMR calculator to lose weight or track how well your diet and exercise routine are working for you.

BMR Calculation Formula- The Harris-Benedict equation revised by Roza and Shixgal

To calculate your BMR, you need to know your weight, height, age, and gender and add those details to the basal metabolic rate formula (like the one below) to determine how many calories you need to burn daily to maintain normal healthy physiology.

Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)

Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)

This calculation is not always accurate because it does not consider other activities or exercises and variables such as muscle mass, diet, weather, genetics, pregnancy, and supplements. However, it can provide a good estimate. 

Factors influencing BMR

Many factors contribute to your BMR, such as:

  • Body surface area 

    Taller adults have more metabolising tissue than shorter-statured ones, which means they burn more calories—leading to a higher BMR.
  • Starving, fasting, or crash dieting

    If you consume fewer kilocalories,  the body slows its metabolism (the rate at which it burns energy) to conserve energy. The loss of lean muscle tissue also leads to a drop in BMR.
  • Age

    Metabolism rate varies from person to person. The most significant factor that affects BMR is age. Children have faster metabolic rates than adults. As we age, our metabolism slows due to hormonal and physiological changes and the loss of muscle tissue. After age 20, the basal metabolic rate (BMR) decreases by 2 percent per decade.
  • Growth

    Because infants and children grow rapidly, they need more energy per pound of body weight than adults do. 
  • Body fat percentage

    Fat cells consume fewer calories than other body parts—the higher your body fat percentage, the lower your basal metabolic rate (BMR), and vice versa. The male body tends to have a 10-15% higher BMR than the female body.
  • Gender

    Men have a faster metabolism and higher basal metabolic rates than women, who tend to be smaller and have less muscle mass.
  • Genetics

    If you have a family history of obesity, you may be predisposed to weight problems.
  • Hormonal and nervous state of the body

    Hormonal imbalances can decrease or increase BMR. For example, the amount of thyroxine in the body also affects basal metabolic rate: a higher level of thyroxine leads to an increased BMR. In contrast, low levels lead to lower metabolism.
  • Pregnancy

    Many changes occur in a woman's body during pregnancy. The higher rate of metabolism that occurs during late pregnancy is associated with the metabolism of the foetus.
  • Certain drugs

    such as caffeine and nicotine, can increase BMR (basal metabolic rate) regardless of your diet. Medications such as antidepressants and steroids also tend to cause weight gain because they impact normal body functions. Body fat redistribution caused by drugs can either increase central adiposity, visceral fat accumulation, or subcutaneous atrophy.
  • Diet

    Dietary deficiencies and changes in metabolism are linked. For example, a diet low in iodine can cause thyroid problems, slowing the metabolic process.
  • Body temperature

    The body's metabolic rate increases by about 15 percent for every degree of rise in the internal temperature. So a patient with a fever of 42°C would have an increase in BMR of 50 percent.
  • Environment effect

    The BMR increases when the temperature is low or high because it takes more work to maintain average body temperature in these conditions.
  • Response to illness or infection

    BMR increases during illness because the body has to devote more resources to tissue growth and immune response.
  • Lean muscles and daily physical activities

    Lean muscle tissues are metabolically active and burn kilocalories rapidly. Physical activities and exercise increase muscle efficiency, causing muscles to burn more kilocalories at rest, which increases BMR.

Resting Metabolic Rate

The energy you expend when your body is at rest is known as resting metabolic rate (RMR) or resting energy expenditure, accounting for most calories you burn daily.

RMR is typically defined as the number of calories a person burns at rest every day—without doing any physical activities or exercise.

Resting metabolic rate (RMR) differs from basal metabolic rate (BMR)- BMR is usually measured in the morning, after an overnight fast, and after no exercise for 24 hours.

Essentially, basal metabolic rate is just the energy your body uses at rest to keep vital organs going—like your heart and lungs whereas resting metabolic rate includes the extra energy expended on non-exercise daily movements—like getting out of bed, chewing or watching tv —resting metabolic rate (RMR) is generally slightly higher than basal metabolic rate.

So if you want to know how many calories you burn in a day, then you can use our online BMR calculator, but if you want to know how many calories you burn in an hour of doing something active like walking around or playing sports, then use RMR since BMR will be much lower.


The BMR calculator is an easy way to determine your calorie needs- it can give you a baseline for how many calories you need to eat every day to maintain your weight. It's not an exact measurement, but it gives you a good idea of where to start while determining your calorie consumption.

If you want to know your exact BMR calories or confirm that the figures are correct for your body type, contact our nutritionist (nutrition daily link). They will be able to help and guide you.

Checkout our BMI Calculator