BMR Calculator
Find your resting calorie burn using two validated formulas.
Average of Mifflin-St Jeor and Harris-Benedict
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Your Basal Metabolic Rate is the number of calories your body burns at complete rest, just to keep you alive. This calculator uses two formulas and shows you both results alongside their average. Here is how to use it:
- Choose your unit system. Imperial uses pounds and inches; Metric uses kilograms and centimeters.
- Enter your weight and height. Use your current measurements, not your goal weight.
- Enter your age and biological sex. Both formulas use sex-specific constants to account for average differences in lean body mass between males and females.
- Read the results. The average of the two formulas is shown as the primary result. The breakdown shows each formula separately so you can see how they compare for your stats.
To find your total daily calorie needs, use the TDEE Calculator, which multiplies your BMR by an activity factor.
About the BMR Formulas
The Mifflin-St Jeor equation (published 1990) is the formula most registered dietitians and research studies recommend for estimating BMR. It tends to give slightly lower, more accurate values for most modern adults than the older Harris-Benedict formula. Male formula: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5. Female formula: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161.
The Harris-Benedict equation (revised 1984) is the historically dominant formula and is still widely used in clinical settings. It tends to run slightly higher than Mifflin. Male formula: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) - 5.677 × age. Female formula: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) - 4.330 × age. Averaging both gives a more robust estimate than relying on either alone.
Frequently Asked Questions
Which BMR formula is more accurate, Mifflin or Harris-Benedict?
Research consistently shows that the Mifflin-St Jeor equation is more accurate for most people, particularly for individuals of average body composition. Harris-Benedict was developed in the early 1900s on a small, primarily athletic sample and tends to overestimate BMR. However, the two formulas agree within 5-8% for most adults, which is why averaging them reduces the impact of individual formula bias.
Does muscle mass affect BMR?
Yes, significantly. Muscle tissue burns more calories at rest than fat tissue. A person with more lean muscle mass will have a higher BMR than someone of the same weight with more body fat. This is one reason strength training is often recommended for long-term weight management: more muscle means a higher resting calorie burn, making it easier to maintain a healthy weight over time.
Can I lose weight by eating at my BMR?
Eating exactly at your BMR means consuming only the calories you need at complete rest, ignoring all daily activity. This creates a significant calorie deficit for most people, which will cause weight loss. However, eating at or below BMR for extended periods is generally not recommended without medical supervision, as it can cause muscle loss, nutrient deficiencies, and metabolic adaptation. Most health guidelines suggest eating at or slightly below your TDEE instead.
Why does BMR decrease with age?
BMR typically decreases with age primarily because of a natural loss of muscle mass (sarcopenia) that begins in the 30s and accelerates after 60. Hormonal changes also play a role, particularly decreasing levels of growth hormone and testosterone in both men and women. Regular resistance training is the most effective way to slow this decline by preserving muscle mass as you age.