BMR Calculator
Estimate your basal metabolic rate, the energy your body uses at rest, with the Mifflin–St Jeor equation, in kg and cm or pounds, feet and inches. It also shows estimated daily calories by activity level.
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How do I calculate my BMR?
BMR is estimated with the Mifflin–St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age in years, plus 5 for men or minus 161 for women. A 30-year-old man weighing 70 kg at 175 cm gets 1,649 kcal a day. It is an estimate, not a measurement.
- Choose metric (kg, cm) or imperial (lb, ft, in) units, and the version of the formula: male or female.
- Enter your age in years, your weight and your height.
- Read your estimated BMR in kcal and kJ per day, and the estimated daily calories for each activity level.
Formulas & Methods
Mifflin–St Jeor, men
Example: 700 + 1,093.75 − 150 + 5 = 1,648.75 kcal
Mifflin–St Jeor, women
Example: 60 kg, 165 cm, 25: 600 + 1,031.25 − 125 − 161 = 1,345.25 kcal
Daily energy estimate
Example: 1,345.25 × 1.55 = 2,085 kcal for moderate activity
Key features
A documented formula
Mifflin–St Jeor (1990), the equation most often recommended for estimating resting energy use in healthy adults.
Metric or imperial
Pounds, feet and inches are converted exactly, the same way as in the BMI Calculator.
Activity levels side by side
Estimated daily calories for all five common activity levels, so you can see the range rather than one number.
kcal and kJ
Results in kilocalories, with kilojoules for countries that label food that way.
What BMR can and can’t tell you
BMR is the energy your body would use in a day at complete rest, for breathing, circulation and keeping warm. The equation predicts it from weight, height, age and sex, and for most healthy adults it lands within about 10% of a measured value; for some people the difference is larger, because muscle mass, health conditions, medication, pregnancy and genetics all play a part.
The activity factors are rough, commonly used multipliers rather than measurements. Use the results as a starting point, and talk to a doctor or a registered dietitian before making significant changes to what you eat.
Frequently Asked Questions
What is the difference between BMR and BMI?
BMI compares weight with height as a screening measure. BMR estimates how much energy your body uses at rest each day. The same BMI can go with quite different BMRs, depending on age, sex and height.
Why does the formula ask for male or female?
The study behind the equation fitted separate constants for men and women, mainly reflecting average differences in body composition. If neither version fits you well, treat the result as a rough range between the two.
Why does BMR go down with age?
The equation subtracts 5 kcal for each year of age, reflecting the average fall in resting energy use as people get older, largely from loss of muscle mass.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241–247 (PubMed)
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc 2005;105(5):775–789 (PubMed)
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