A Basal Metabolic Rate (BMR) calculator is a tool that calculates how many calories your body needs for a full day of bodily processes. It calculates a BMR score using your gender, weight, height, and age. 

You can find out more about Basal Metabolic Rates, the Mifflin St Jeor equation, and the formulas for calculating it below.

What is Basal Metabolic Rate (BMR)?

Your basal metabolic rate is the volume of energy your body requires for everyday bodily functions such as breathing, body temperature, brain/nerve functions, and more. 

Your basal metabolic rate makes up around 75 percent of your daily calorie usage, but it can vary from one person to the next. The energy you require for these functions also gets lower as you get older or as your lean body mass decreases. If, however, you increase your muscle mass, your basal metabolic rate will increase. 

The use of the BMR calculator also involves your metabolism. Your metabolism is a chemical reaction that helps you to turn food into energy to stay alive.

The Basal Metabolic Rate Calculator

Knowing your BMR gives you an idea of the calories you need to give your body every day, but working it out by hand is time-consuming. Instead, you can use a basal metabolic rate calculator to speed up the process.

Using the BMR Formula to Calculate Your Basal Metabolic Rate

There are several ways in which to calculate your BMR, but if you want the most accurate answer, you will find the Mifflin St Jeor equation is the best. 

The formula is as follows: 

BMR = (10 x weight / 1kg + 6.25 x height / 1cm – 5 x age / 1 year + s) / kcal / day

S = +5 for males and – 161 for females 

Over the years, there have been several methods for working out your BMR, but with varying degrees of accuracy. In 1919, the Harris-Benedict equation became the most accurate of its time and that did not change for over seven decades. 

The Basal Metabolic Rate called Mifflin St Jeor equation then turned out to be even more accurate, so the world is in a transitional phase between Harris-Benedict and Mifflin St Jeor. If you wanted to know your resting daily energy expenditure or RDEE, you could also use the third possible equation, Katch-McArdle.

Because Mifflin St Jeor is the most accurate, we will use it for all our equations – and our BMR calculator. If you consider yourself to be a bit of a gym bunny, you can also try out a BMI calculator or a calorie calculator to keep on top of daily weight management.