Basal Metabolic Rate Calculator
Calculate your BMR using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle formulas. Find your TDEE, daily caloric needs, and macronutrient targets.
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Basal Metabolic Rate Calculator
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Formula: Mifflin-St Jeor: BMR = (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + s
Worked example — BMR = 1,749 kcal/day | TDEE = 2,711 kcal/day
Formula
Mifflin-St Jeor: BMR = (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + s
Where s = +5 for males and -161 for females. Weight is in kilograms, height in centimeters, age in years. TDEE = BMR x Activity Multiplier (1.2 sedentary to 1.9 very active). The Mifflin-St Jeor equation is recommended by the Academy of Nutrition and Dietetics as the most accurate for healthy adults.
Worked Examples
Example 1: BMR for a 30-Year-Old Male
Problem:Calculate BMR for a 30-year-old male, 175 cm tall, weighing 80 kg, moderately active.
Solution:Mifflin-St Jeor: BMR = (10 x 80) + (6.25 x 175) - (5 x 30) + 5 BMR = 800 + 1093.75 - 150 + 5 = 1,748.75 kcal/day TDEE = 1,749 x 1.55 (moderate activity) = 2,711 kcal/day
Result:BMR = 1,749 kcal/day | TDEE = 2,711 kcal/day
Example 2: BMR for a 25-Year-Old Female
Problem:Calculate BMR for a 25-year-old female, 163 cm tall, weighing 60 kg, lightly active.
Solution:Mifflin-St Jeor: BMR = (10 x 60) + (6.25 x 163) - (5 x 25) - 161 BMR = 600 + 1018.75 - 125 - 161 = 1,332.75 kcal/day TDEE = 1,333 x 1.375 (light activity) = 1,833 kcal/day
Result:BMR = 1,333 kcal/day | TDEE = 1,833 kcal/day
Example 3: Male BMR example
Problem:A 30-year-old male is 175 cm tall, weighs 80 kg, and is moderately active.
Solution:Using Mifflin-St Jeor, the BMR estimate is about 1,749 kcal/day. Multiplying by a moderate activity factor gives a TDEE near 2,711 kcal/day.
Result:BMR: about 1,749 kcal/day | TDEE: about 2,711 kcal/day
Frequently Asked Questions
What is basal metabolic rate?
Basal metabolic rate is the energy your body uses at rest to support essential processes such as breathing, circulation, and temperature regulation. It is the baseline part of your daily calorie burn.
What is the difference between BMR and TDEE?
BMR is your resting calorie use. TDEE starts with BMR and then adds movement, exercise, and daily activity. TDEE is the more practical number for maintenance, fat loss, and gain plans.
Which BMR formula should I trust most?
Mifflin-St Jeor is a strong default for many adults, while other formulas can be useful for comparison. The best approach is to treat any formula as an estimate and then compare it with real-world weight trends.
How should I use BMR for weight management?
BMR helps you understand your baseline energy needs, but most meal planning decisions are based on TDEE. From there, a small deficit or surplus can be added depending on whether the goal is fat loss, maintenance, or weight gain.
How does the Katch-McArdle formula differ from Mifflin-St Jeor?
Mifflin-St Jeor works from total body weight, height, age and sex, so it cannot tell muscle from fat. Katch-McArdle instead uses lean body mass alone, in the form BMR = 370 + 21.6 x LBM in kilograms, on the reasoning that fat-free tissue drives most resting energy use. That makes it the better choice for lean or heavily muscled people who have a measured body fat percentage, and a poor choice when the body fat figure is itself only an estimate.
What is the thermic effect of food, and why does it sit outside BMR?
The thermic effect of food is the energy spent digesting, absorbing and storing what you eat. BMR is defined under fasted resting conditions, so this cost is excluded by definition and is instead bundled into TDEE along with activity. It is commonly estimated at roughly a tenth of calories consumed, and it is not uniform: protein carries a noticeably higher thermic cost than fat or carbohydrate, which is one reason higher-protein diets feel less efficient at storing energy.
Why does the activity multiplier affect the result more than the choice of formula?
The three BMR equations usually land within a few per cent of each other for the same person. The activity multiplier ranges from 1.2 for sedentary to 1.9 for very active, a spread of well over fifty per cent on top of the same BMR. Choosing a multiplier that flatters your week is therefore the largest source of error in a TDEE estimate, and the usual fix is to pick a conservative level and correct it against real weight trends.
What is the difference between BMR and resting metabolic rate?
BMR is measured under strict laboratory conditions: an overnight fast, full rest, a thermoneutral room and no recent exertion. RMR is measured under looser conditions that are easier to arrange in a clinic, so it captures a little residual digestion and movement and reads slightly higher than true BMR. The two terms are used almost interchangeably in everyday nutrition tools, and the equations differ in what they were fitted to: Mifflin-St Jeor was derived from resting measurements, while Harris-Benedict was built on basal ones.
Why can BMR fall during a long period of dieting?
Two things happen at once. Losing weight removes both fat and some fat-free mass, and a smaller body genuinely needs fewer calories at rest, which the equation reflects through the weight term. On top of that sits adaptive thermogenesis, a downward shift in energy use beyond what the size change predicts, driven partly by hormonal signalling. The practical consequence is that a deficit set once will shrink over time and needs recalculating as weight changes.
Why do sex and age change BMR in these equations?
Both act mostly through body composition. The sex constant in Mifflin-St Jeor, plus five for males and minus 161 for females, stands in for the average difference in fat-free mass at the same height and weight. The age term subtracts five calories per year, approximating the gradual loss of muscle across adulthood. Neither term is destiny: an older person who maintains muscle through resistance training will run above what the formula predicts.
References
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist · Editorial policy
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