This tool is for informational purposes only and does not constitute medical advice. Always consult a healthcare professional.
How the BMR Calculator Works
This BMR calculator provides results from two of the most widely used metabolic rate equations: the Mifflin-St Jeor equation (1990) and the revised Harris-Benedict equation (1984). Both estimate the number of calories your body burns at complete rest to maintain essential functions like breathing, circulation, and cell production. Your BMR typically represents 60-75% of your total daily energy expenditure.
Understanding your BMR is the foundation of any nutrition or fitness plan. Once you know your resting calorie burn, you can multiply it by an activity factor to find your Total Daily Energy Expenditure (TDEE). Use our Calorie Calculator to determine your TDEE and recommended daily calorie intake based on your activity level and goals.
How to Use This Tool
- Enter your age — BMR changes with age, decreasing as you get older.
- Select your gender — men and women have different metabolic rate formulas.
- Enter your height and weight — provide these in centimetres and kilograms.
- Click Calculate BMR — results from both formulas appear instantly, along with the difference between them.
- Use your BMR — visit the Calorie Calculator to find your TDEE based on your BMR and activity level.
How It Works Behind the Scenes
The Mifflin-St Jeor equation: Men BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5. Women BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161. The revised Harris-Benedict equation: Men BMR = (13.397 x weight) + (4.799 x height) - (5.677 x age) + 88.362. Women BMR = (9.247 x weight) + (3.098 x height) - (4.330 x age) + 447.593.
Both formulas use the same four inputs (age, gender, height, weight) but apply different coefficients. The Mifflin-St Jeor equation is generally recommended by the Academy of Nutrition and Dietetics as the most accurate for estimating BMR in healthy adults. The Harris-Benedict equation tends to give slightly higher values. The calculator displays both results so you can see the range and choose which to use as your baseline.
Frequently Asked Questions
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate is the number of calories your body burns at complete rest to maintain essential life functions such as breathing, blood circulation, cell production, and nutrient processing. It represents the minimum energy your body needs to survive if you were lying in bed all day without moving. BMR typically accounts for 60-75% of your total daily energy expenditure, making it the largest component of your daily calorie burn.
What is the difference between Mifflin-St Jeor and Harris-Benedict?
Both are equations for estimating BMR, developed at different times using different study populations. The original Harris-Benedict equation was published in 1919 and revised in 1984 by Roza and Shizgal. The Mifflin-St Jeor equation was published in 1990 and is generally considered more accurate for modern populations. The Academy of Nutrition and Dietetics recommends Mifflin-St Jeor as the most reliable formula for estimating BMR in healthy individuals.
How can I use my BMR to plan my diet?
Your BMR tells you the minimum calories your body needs at rest. To find your total daily calorie needs (TDEE), multiply your BMR by an activity factor that reflects your exercise habits. Visit our Calorie Calculator for this step. Your TDEE is the number of calories needed to maintain your current weight. To lose weight, eat moderately below your TDEE; to gain, eat above it. Never eat below your BMR without medical supervision.
What factors affect BMR?
Several factors influence your BMR. Age is significant as BMR decreases with age due to muscle loss. Gender matters because men typically have higher BMR from greater muscle mass. Body composition plays a major role since muscle burns more calories than fat. Height and weight directly affect the calculation. Genetics, hormonal balance (particularly thyroid function), and environmental temperature also influence BMR but are not captured by the equations.
Why does BMR decrease with age?
BMR decreases with age primarily due to the gradual loss of lean muscle mass known as sarcopenia. Starting around age 30, adults typically lose 3-8% of muscle mass per decade if they do not actively maintain it through strength training. Since muscle tissue is metabolically active and burns significantly more calories at rest than fat tissue, this muscle loss directly reduces resting energy needs. Regular resistance training can slow this decline.
Is my data stored?
No. All calculations happen entirely in your browser using JavaScript. Your age, gender, height, weight, and calculated results are never transmitted to any server or stored in any database. Once you close or refresh the page, all entered data is gone. Daytics protects your privacy by operating all tools completely client-side with no data collection or tracking of any kind.
