BMR Calculator: Calculate Your Basal Metabolic Rate
Use the FitZio BMR Calculator to estimate how many calories your body needs at rest. Enter your age, sex, height, and weight to calculate your estimated Basal Metabolic Rate using the Mifflin-St Jeor equation.
Calculate Your BMR
Enter your information below to estimate your Basal Metabolic Rate.
Your BMR is an estimate of the energy your body would use at rest to support essential physiological functions. It does not include the calories you burn through normal daily activity or exercise.
What Is BMR?
BMR stands for Basal Metabolic Rate. It represents an estimate of the amount of energy your body requires while at rest to maintain essential physiological functions.
Your body continuously uses energy even when you are not exercising. Breathing, circulation, maintaining body temperature, and supporting normal organ function all require energy.
A BMR calculator uses measurable information such as age, height, weight, and sex to estimate this resting energy requirement. It is a useful starting point for understanding daily calorie needs, but it should not be treated as a direct measurement of your metabolism.
BMR vs TDEE: What’s the Difference?
BMR
Estimates the calories your body needs at rest for essential physiological functions.
TDEE
Estimates your total daily energy expenditure after accounting for your activity level.
BMR is therefore one component used when estimating your overall daily calorie requirements. If you want an estimate that accounts for your normal activity, use the FitZio TDEE Calculator.
How FitZio Calculates BMR
FitZio uses the Mifflin-St Jeor equation to estimate Basal Metabolic Rate.
The equation uses body weight, height, and age, with a different constant for males and females.
The Mifflin-St Jeor equation was published in 1990 and was developed from measurements in healthy adults. FitZio uses it as the single methodology for this calculator so the calculation remains transparent and reproducible.
BMR Calculation Example
Suppose a 30-year-old woman weighs 70 kg and is 175 cm tall.
BMR = 700 + 1093.75 − 150 − 161
BMR ≈ 1483 kcal/day
This means the equation estimates approximately 1,483 calories per day for resting energy expenditure for this example. It does not mean that the person should automatically eat exactly 1,483 calories per day.
What Does Your BMR Result Mean?
Your BMR result is best understood as a baseline estimate of resting energy expenditure.
It is not your recommended daily calorie intake. Your actual daily energy needs are generally higher because you also use energy through movement, exercise, digestion, and other daily activities.
For example
If your estimated BMR is 1,500 kcal/day, that does not mean your total daily calorie requirement is 1,500 calories. Your total energy expenditure can be substantially higher depending on your activity and other factors.
To estimate total daily calorie needs, continue to the TDEE Calculator.
What Can Affect BMR?
BMR varies between individuals. Factors associated with resting energy expenditure include:
- Body size and weight
- Height
- Age
- Sex
- Body composition
- Physiological and health factors
- Environmental and other individual factors
A calculator cannot capture every factor that affects an individual’s actual resting energy expenditure. That is why the result should be treated as an estimate rather than a laboratory measurement.
How Accurate Is a BMR Calculator?
A BMR calculator provides an estimate rather than a direct measurement. Predictive equations can be useful for estimating resting energy requirements, but individual results can differ from measured energy expenditure.
Your calculated BMR should therefore be used as a starting point rather than an exact number. If your calorie needs are important for a specific medical or nutritional situation, a qualified healthcare or nutrition professional can provide individualized guidance.
Can BMR Help With Weight Management?
BMR can help you understand the resting component of your energy expenditure, but BMR alone does not tell you how many calories you need to lose, maintain, or gain weight.
For weight-management planning, an estimate of total daily energy expenditure is more useful because it incorporates activity.
Start with your BMR here, then use the TDEE Calculator to estimate your daily energy expenditure.
When Should You Recalculate Your BMR?
Your estimated BMR can change as your body measurements and age change. You may want to recalculate when there has been a meaningful change in your body weight or when you are reassessing your calorie needs.
You do not need to calculate BMR repeatedly throughout the same day. The calculator is most useful when your underlying measurements have meaningfully changed.
BMR Calculator Limitations
- The result is an estimate, not a direct measurement of metabolism.
- The Mifflin-St Jeor equation does not account for every individual physiological factor.
- BMR is not the same as total daily calorie expenditure.
- BMR should not be interpreted as a personalized calorie prescription.
- People with specific medical, nutritional, pregnancy-related, or eating-disorder concerns should seek individualized professional guidance rather than relying solely on a calculator.
Frequently Asked Questions About BMR
What does BMR stand for?
BMR stands for Basal Metabolic Rate. It is an estimate of the energy your body requires at rest to support essential physiological functions.
How do I calculate my BMR?
You can calculate your estimated BMR using the Mifflin-St Jeor equation. FitZio’s BMR Calculator performs the calculation for you after you enter your age, sex, height, and weight.
What is a normal BMR?
There is no single normal BMR value that applies to everyone. Resting energy requirements vary according to factors such as body size, height, age, sex, and body composition.
Is BMR the same as maintenance calories?
No. BMR estimates energy expenditure at rest. Maintenance calories generally refer to the approximate amount of energy required to maintain body weight while accounting for total daily activity. Use a TDEE calculation for that estimate.
Does BMR include exercise?
No. BMR represents resting energy expenditure and does not include calories burned through exercise or ordinary daily movement.
Does BMR change when I lose weight?
It can. Changes in body size and composition can affect estimated resting energy expenditure, so recalculating after a meaningful change in body weight can provide an updated estimate.
Which BMR formula does FitZio use?
FitZio uses the Mifflin-St Jeor equation for this BMR Calculator.
Can BMR tell me how many calories I should eat?
Not by itself. BMR represents resting energy expenditure. Your actual daily calorie needs also depend on activity and other factors. Use your BMR as a starting estimate rather than as a direct calorie prescription.
Is a BMR calculator accurate?
A BMR calculator provides an estimate. Individual energy expenditure can differ from an equation-based prediction, so the result should not be treated as an exact measurement.
What is the difference between BMR and TDEE?
BMR estimates energy expenditure at rest, while TDEE estimates total daily energy expenditure after accounting for activity. You can use the FitZio TDEE Calculator after calculating your BMR.
Related FitZio Calculators
Note: Some related calculator pages may still be under development. Keep these links active only after the corresponding FitZio pages are published.
Key Takeaway
Your Basal Metabolic Rate is an estimate of the energy your body uses at rest. The FitZio BMR Calculator uses the Mifflin-St Jeor equation to estimate this value from your age, sex, height, and weight.
Remember that BMR is only a resting-energy estimate. If you want to estimate your total daily calorie expenditure, use the FitZio TDEE Calculator.
Methodology & Source
This calculator uses the Mifflin-St Jeor equation for estimating resting energy expenditure.
The original Mifflin-St Jeor research was published in the American Journal of Clinical Nutrition in 1990.
Use the BMR Calculator as Your Starting Point
The FitZio BMR Calculator gives you a practical starting point for understanding your estimated daily energy needs at rest. Your BMR can help you understand how many calories your body may use to support essential functions, while your actual daily calorie needs also depend on movement and activity. For a more complete estimate, use your BMR result with the FitZio TDEE Calculator to estimate your total daily energy expenditure. Whether you are working toward weight management, improving your nutrition, or simply learning more about your metabolism, the BMR Calculator can help you better understand your body's estimated energy requirements.
