Basal Metabolic Rate Calculator
Enter your age, height, sex, and weight to find your basal metabolic rate.
What is the Basal Metabolic Rate?
Basal Metabolic Rate (BMR) is the amount of energy your body needs to carry out the most basic functions in a resting state. This is calculated using a formula and is based on certain physical characteristics that are unique to your body.
We all need the energy to fuel our bodily functions like heartbeat, breathing, nervous system communication, digestion, the endocrine system, and more. Even when you are asleep, your body burns energy.
Calories are Energy
The power source for your body is calories. The amount of calories a person burns to fuel basic bodily functions is their basal metabolic rate (BMR) and varies by the individual.
BMR can vary depending on certain factors, including the following factors
- Height
- Weight
- Body composition
- Age
- Gender
For example, muscle burns more calories at rest than fat. So, if you have more muscle than fat, then your BMR will be higher than someone with more body fat.
How to Calculate Basal Metabolic Rate
There are two main methods for calculating the basal metabolic rate, Harris-Benedict, and Mifflin St Jeor.
Harris-Benedict Basal Metabolic Rate Formula
This formula has been used since 1919 and delivers an estimate of how much energy your body needs to stay alive.
History of Harris-Benedict Formula
This equation came as a result of a study performed by James Arthur Harris and Francis Gano Benedict. It was later published by the Carnegie Institution of Washington in the publication, “A Biometric Study of Basal Metabolism in Man.”
Harris-Benedict Equation
For males the equation is as follows:
BMR = 66.47 + (13.75 x weight in kilograms) + (5.003 x height in centimeters) – (6.755 x age in years)
For females the equation is as follows:
BMR = 655.1 + (9.563 x weight in kilograms) + (1.85 x height in centimeters) – (4.676 x age in years)
To calculate the BMR, simply follow the equations. These equations are based on the metric system so use kilograms for your weight and centimeters for your height.
Example of Harris-Benedict BMR for a 45-year-old woman weighing 70kg at a height of 180cm.
655.1 + (9.563 x 70) + (1.85 x 180) – (4.676 x 45) = 1,447.09 BMR
The BMR refers to the amount of energy (in calories) your body burns if you were lying down all day, with no activity.
Mifflin-St. Jeor Basal Metabolic Rate Equation
The Mifflin-St. Jeor Formula (or equation) calculates your basal metabolic rate (BMR), the results are based on an estimated average. Basal metabolic rate is the amount of energy expended per day at rest (how many calories you would burn on bed rest).
Mifflin – St. Jeor Basal Equation
For males the equation is as follows:
BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) + 5
For females the equation is as follows:
BMR = (10 x weight in kilograms) + (6.25 x height in centimeters) – (5 x age in years) – 161
Example of Mifflin-St. Jeor BMR for a 32-year-old woman weighing 70kg at a height of 180cm.
(10 x 70) + (6.25 x 180) – (5 x 45) – 161 = 1,439 BMR
As you will see, the results based on the same 45-year-old, 70kg, 180cm woman are very similar.
What is a “Good” BMR?
The short answer is there is no ‘good BMR’. This is because every person’s BMR is different. It’s factored by age, gender, body size, height, weight, and mass – including the size of your internal organs.
Low BMR means your body requires fewer calories to sustain life-giving functions. It also means you need to eat fewer calories to lose weight than someone with a higher BMR.
Things like illness, exercise, drugs (including nicotine), and even stress levels and anxiety can all boost your BMR.
How to Use BMR to Lose Weight
Your BMR is a helpful tool in determining the number of calories you should cut from your diet to lose weight safely.
Your basal metabolic rate isn’t a diet tool in itself – but knowing your BMR can help prevent you from restricting too many calories from your diet, which can make you feel fatigued, lethargic, irritable, and hangry (hungry and angry).
Steps to Lose Weight with BMR
- First step, calculate your personal BMR. (This will tell you the minimum number of calories you should get each day.)
- Next, you also need to know how many calories you need each day to maintain your current weight, so you can subtract calories accordingly to determine the ideal daily calorie limit for you.
The number should be somewhere between your BMR and the number of calories you need to maintain your current weight.
The average man needs about 2,500 calories and the average woman needs 2,000 calories a day to maintain their weight.
You should also take into account your level of physical activity. If you exercise regularly, you won’t need to cut as many calories to lose weight as someone with a more sedentary life or who doesn’t work out.
For weight loss, create a daily deficit of no more than 500 – 600 calories. This will ensure steady and sustainable weight loss. Aim to lose about 0.5 to 1kg (1 to 2lb) a week until you reach a healthy weight for your height.
Keep in mind, most people need over 1,000 calories each day just to maintain their basic functions. This is why restrictive ‘crash’ diets are really bad news for your body. Not getting enough energy each day can interfere with your body’s basic processes, such as causing reduced brain function, low blood pressure, or abnormal heart rate.
So, you should always take in, as a minimum, the number of calories you need to maintain basic functions as indicated by your BMR.
