BMR Calculator
Calculate your basal metabolic rate (BMR) to estimate how many calories your body uses at rest. Compare popular formulas and explore estimated daily calorie needs for different activity levels.
Enter your details
For an estimate based on your measurements
Your BMR results
Estimated calories and formula comparison
Estimated energy used at rest, not a daily calorie target.
Compare resting energy with estimated total daily needs at your selected activity level.
Different published equations can produce different estimates from the same measurements.
| Formula | Estimated BMR |
|---|---|
| Mifflin-St Jeor | — |
| Revised Harris-Benedict | — |
| Katch-McArdle | Enter body fat % |
What is basal metabolic rate (BMR)?
Basal metabolic rate, or BMR, is the energy your body needs to support essential functions while at rest, such as breathing, circulation, maintaining body temperature, and supporting organs. A BMR calculator estimates this energy in calories per day using details such as age, sex, height, and weight.
Your BMR is not the same as the number of calories you burn over a whole day. Walking, work, exercise, and digestion add to your energy use. That is why the result also estimates total daily energy expenditure (TDEE) using the activity level you select.
BMR
Energy your body uses at rest to maintain essential functions.
TDEE
Estimated total daily energy expenditure after accounting for activity.
Daily calorie needs
A practical starting estimate for maintenance planning, not a prescription.
How to calculate BMR
This calculator uses the Mifflin-St Jeor equation as its primary estimate and also displays the revised Harris-Benedict equation. If you enter a body fat percentage, it calculates Katch-McArdle as an additional comparison. The equations estimate resting energy; they do not directly measure metabolism.
Mifflin-St Jeor equation
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Revised Harris-Benedict equation
Women: 447.593 + 9.247 × weight (kg) + 3.098 × height (cm) − 4.330 × age
Katch-McArdle equation
Katch-McArdle requires a body fat estimate to calculate lean body mass. The equations can disagree, so treat the results as estimates rather than exact calorie requirements.
BMR vs. TDEE: What is the difference?
BMR estimates calories used at rest. TDEE estimates the total calories used across the day, including movement and exercise. To estimate TDEE, a common approach is to multiply BMR by an activity factor. This page uses factors from 1.2 for sedentary activity to 1.9 for extra-active routines.
Your TDEE is generally the more useful starting point when planning daily calorie intake. Eating exactly at your BMR is not automatically the right goal for weight loss, maintenance, or muscle gain. Individual needs differ, and calculator results should be adjusted using real-world progress and appropriate professional advice.
How to use this BMR calculator
- Select metric units or US customary units.
- Choose male or female for the equation, then enter age, height, and weight.
- Select the activity level that best describes your usual routine to estimate daily calorie needs.
- Optionally enter a known body fat percentage to compare the Katch-McArdle equation.
- Select Calculate BMR and review the results, chart, and formula comparison.
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Frequently asked questions
What is a normal BMR?
There is no single normal BMR value. It varies with age, sex, height, weight, and body composition. Compare your estimate with your own needs rather than using another person’s number as a target.
Which BMR formula is best?
Mifflin-St Jeor is commonly used as a general starting estimate for adults. Harris-Benedict offers a comparison, while Katch-McArdle uses lean body mass and requires a body fat estimate. No equation is exact for every person.
How do I calculate BMR manually?
Convert weight to kilograms and height to centimeters, then use the Mifflin-St Jeor equation shown above with your age and the appropriate sex-specific constant.
Is BMR the same as calories I should eat?
No. BMR estimates energy used at rest. Your total daily energy expenditure includes activity, so TDEE is generally a better starting estimate for daily calorie planning.
Does BMR decrease with age?
BMR often changes with age, partly because body composition and muscle mass may change, but the amount varies by person. The calculator’s equation includes age as one of several factors.
How accurate is an online BMR calculator?
It provides an estimate based on a published equation, not a laboratory measurement. Actual energy needs can differ due to body composition, health, and other individual factors.
Important: This BMR calculator is for general educational purposes and does not provide medical advice. Do not use an estimated BMR alone to set a restrictive diet. Consult a qualified healthcare professional or registered dietitian for individualized guidance.