BMR & Calorie Calculator
Calculate your Basal Metabolic Rate (BMR) and daily calorie needs using the Mifflin-St Jeor equation. Get personalized recommendations for your fitness goals.
How BMR Is Calculated
Mifflin-St Jeor Equation:
Male: BMR = (4.536 × Weight) + (15.88 × Height) − (5 × Age) + 5
Female: BMR = (4.536 × Weight) + (15.88 × Height) − (5 × Age) − 161
Weight in lbs · Height in inches · Age in years
The Mifflin-St Jeor equation is one of the most commonly used predictive equations for estimating resting energy expenditure in healthy adults.
Your BMR & Calorie Results
Analysis completeMacronutrient Breakdown
| Goal | Protein | Carbs | Fat |
|---|---|---|---|
| 🔵 Weight Loss | — | — | — |
| 🟢 Maintenance | — | — | — |
| 🟠 Muscle Gain | — | — | — |
Suggested Meal Distribution
Estimated Goal Timeline
About Calorie Deficit
A daily calorie deficit of approximately 500 kcal may support gradual weight loss for many adults. Individual results vary based on metabolism, activity, and body composition.
Maintenance Advice
- 🥩 Maintain adequate protein intake
- 🏃 Exercise regularly
- 😴 Sleep adequately
- 📊 Monitor progress weekly
Expected Weekly Rate
≈ 0.25–0.5 kg/week
Food Examples
Formula Source
The Mifflin-St Jeor equation is one of the most commonly used predictive equations for estimating resting energy expenditure in healthy adults. Originally published in the American Journal of Clinical Nutrition (1990).
Personal Factors
BMR Level
Daily Calorie Needs by Activity Level
Your Details
What This Means
Your BMR is the minimum calories your body needs at rest. TDEE includes all daily activities. Use the goal cards to plan your nutrition.
How This Calculator Works
Basal Metabolic Rate (BMR) is the number of calories your body burns at rest to maintain vital functions.
Mifflin-St Jeor Equation (1990):
Male: BMR = (4.536 × Weight) + (15.88 × Height) − (5 × Age) + 5
Female: BMR = (4.536 × Weight) + (15.88 × Height) − (5 × Age) − 161
Total Daily Energy Expenditure (TDEE):
TDEE = BMR × Activity Factor
Activity Factors:
• Sedentary: 1.2
• Lightly Active: 1.375
• Moderately Active: 1.55
• Very Active: 1.725
• Extra Active: 1.9
Real Examples
Limitations
- • Calorie estimates are approximations, not exact measurements
- • Individual metabolism varies based on genetics and body composition
- • These formulas may not apply to athletes or those with high muscle mass
- • Always consult a healthcare professional for personalized nutrition advice
References
Educational information based on established nutrition research.
- Mifflin MD, et al. – A new predictive equation for resting energy expenditure. Am J Clin Nutr. 1990.
- Academy of Nutrition and Dietetics – Calorie Guidelines
- American College of Sports Medicine (ACSM) – Exercise Guidelines
References were selected from recognized nutrition and health sources and are reviewed periodically for accuracy.
Trust & Privacy
All calculations are performed locally in your browser. No personal information is stored or shared.
Editorial Process
The CalculatorKits editorial team reviews this tool periodically for:
- • Formula accuracy
- • Nutrition references
- • Educational content
- • User guidance
Last reviewed: July 2026
Frequently Asked Questions
BMR (Basal Metabolic Rate) is the number of calories your body burns at rest to maintain vital functions like breathing and circulation.
TDEE (Total Daily Energy Expenditure) is BMR multiplied by your activity level. It represents your total daily calorie needs.
It's a widely validated formula for estimating BMR based on age, gender, weight, and height. It's considered one of the most accurate equations.
No. This is an educational tool for general awareness. It should not replace professional medical or nutrition advice.
Recalculate when your weight changes significantly (5+ lbs), your activity level changes, or every 4-6 weeks to adjust your nutrition plan.
📍 © 2026 CalculatorKits — BMR Calculator · For educational use only
BMR Calculator: Calculate Your Basal Metabolic Rate and Daily Calorie Needs
Your body uses energy all day, even when you are not exercising. Breathing, maintaining body temperature, circulating blood, supporting brain activity, and keeping your organs working all require energy. Your BMR Calculator can estimate how many calories your body needs to support these basic functions while at rest.
BMR stands for Basal Metabolic Rate. It is an estimate, not a direct measurement of your metabolism. Still, it can be a useful starting point when you want to understand your energy needs and see how activity changes your estimated daily calorie requirements.
The CalculatorKits BMR Calculator uses the Mifflin St Jeor equation and also considers your activity level and fitness goal. The tool can therefore show both an estimated BMR and an estimated Total Daily Energy Expenditure, or TDEE.
The important part is knowing how to interpret those numbers. A calculated calorie value is not a prescription, and it should not be treated as an exact description of how many calories your body actually burns.
Quick Answer
A BMR Calculator estimates the number of calories your body uses at rest to support essential physiological functions.
The CalculatorKits tool uses the Mifflin St Jeor equation. It asks for your age, gender, height, weight, activity level, and fitness goal. After you calculate, it displays your estimated BMR and TDEE along with additional educational information.
BMR is different from your total daily calorie needs.
Your BMR represents energy used for basic functions at rest. Your TDEE is an estimate of the energy you use across the day after activity is taken into account.
The Mifflin St Jeor equation was developed from measurements of resting energy expenditure in 498 healthy adults and published in 1990.
What Is BMR?
BMR means Basal Metabolic Rate.
It refers to the energy your body needs to maintain basic life sustaining functions when you are at rest under strict conditions.
Your body does not stop using energy simply because you are sitting or sleeping. Your heart continues beating. Your lungs continue working. Your brain remains active. Your body continues regulating temperature and supporting cellular processes.
All of these activities require energy.
That is why BMR is useful when discussing calorie requirements. It gives you a starting point for understanding the energy your body needs before accounting for normal daily movement and exercise.
However, there is an important distinction between strict BMR and resting energy expenditure. In research, basal measurements are taken under tightly controlled conditions. Many online tools use the terms BMR and resting metabolic rate in a practical way, even though the measurement conditions are not identical.
The Mifflin St Jeor equation itself was developed to predict resting energy expenditure rather than directly measure metabolism in a laboratory.
What Is a BMR Calculator?
A BMR Calculator is an online tool that uses a mathematical equation to estimate your resting energy expenditure from basic personal measurements.
The CalculatorKits tool uses age, gender, height, and weight to calculate the estimated BMR. It then uses your selected activity level to estimate TDEE.
This is much easier than manually working through the equation and converting between different measurement units.
The value of a calculator is convenience. The limitation is that the answer is still an estimate.
Your actual resting energy expenditure can differ from the number produced by an equation. Research comparing prediction equations with measured resting energy expenditure has found that Mifflin St Jeor performs well among commonly used equations, but meaningful individual errors can still occur.
How Does the BMR Calculator Work?
The CalculatorKits BMR Calculator uses the Mifflin St Jeor equation.
The calculator displays the formula using pounds and inches.
Formula for Men
BMR = (4.536 × Weight in pounds) + (15.88 × Height in inches) − (5 × Age) + 5
Formula for Women
BMR = (4.536 × Weight in pounds) + (15.88 × Height in inches) − (5 × Age) − 161
The same equation is commonly written using kilograms and centimeters:
For men:
BMR = (10 × Weight in kilograms) + (6.25 × Height in centimeters) − (5 × Age) + 5
For women:
BMR = (10 × Weight in kilograms) + (6.25 × Height in centimeters) − (5 × Age) − 161
The original research used weight in kilograms and height in centimeters. The CalculatorKits version converts the relationship so it can work with pounds and inches.
How to Use the BMR Calculator
The CalculatorKits tool has several fields because it does more than calculate resting energy expenditure. Follow these steps in order.
- Enter your age. Type your current age in years into the Age field.
- Select your gender. Choose Male or Female from the available options.
- Choose your height unit. The height section allows you to select the appropriate measurement system.
- Enter your height. When using the US format, enter your height using feet and inches. When using the metric option, enter the requested metric measurement.
- Choose your weight unit. Select the appropriate unit in the Weight section.
- Enter your weight. Enter your current body weight using the unit you selected.
- Select your activity level. Choose the option that best represents your usual activity. The tool provides five choices: Sedentary, Lightly Active, Moderately Active, Very Active, and Extra Active.
- Choose your fitness goal. Select the goal available in the calculator that best matches what you want to explore.
- Click “Calculate BMR.” The calculator processes your information and displays your estimated BMR and calorie results.
- Review your results. The results section displays BMR, estimated TDEE, activity level, goal information, and additional educational estimates.
- Use “Reset” when needed. This clears the current information so you can start a new calculation.
- Use “Try Example” if you want to see how the tool works. This is useful if you want to explore the calculator before entering your own information.
The most important step is choosing your activity level carefully. A large part of the difference between BMR and TDEE comes from activity.
What Does the BMR Result Mean?
Suppose your calculator estimates your BMR at 1,600 calories per day.
That does not mean you should automatically eat exactly 1,600 calories each day.
It means the equation estimates that your body would use roughly that amount of energy for basic resting functions under the assumptions of the equation.
Your body also uses energy for walking, working, exercising, digesting food, and other daily activities.
That is where TDEE becomes useful.
The CalculatorKits tool calculates TDEE by multiplying BMR by an activity factor. The displayed activity factors range from 1.2 for sedentary activity to 1.9 for extra active activity.
Because activity categories are broad, TDEE is also an estimate rather than a precise measurement.
BMR vs TDEE: What Is the Difference?
BMR and TDEE are related, but they are not the same thing.
BMR is an estimate of energy expenditure at rest.
TDEE is an estimate of total energy expenditure across the day.
A simple way to think about it is:
BMR = resting energy requirement
TDEE = BMR plus the energy associated with your daily activity and other normal energy expenditure
The CalculatorKits tool uses an activity factor to estimate TDEE:
TDEE = BMR × Activity Factor
For example, a person with an estimated BMR of 1,600 calories and a sedentary activity factor of 1.2 would have an estimated TDEE of:
1,600 × 1.2 = 1,920 calories
That number is still only an estimate. Real daily energy expenditure changes with movement, exercise, body composition, routine, and other individual factors.
Understanding the Activity Levels
Choosing the right activity level can make a noticeable difference to your TDEE estimate.
Sedentary
This option is intended for someone with little or no structured exercise and a mostly desk based routine.
Lightly Active
This represents light exercise or physical activity on roughly one to three days per week.
Moderately Active
This represents moderate exercise or activity on roughly three to five days per week.
Very Active
This is intended for people performing harder exercise or substantial physical activity most days.
Extra Active
This option is intended for athletes or people whose work involves significant physical demands.
The labels are useful categories, not precise measurements. Someone who exercises three days a week but spends most of the remaining day sitting may have a very different energy expenditure from someone who is physically active throughout the day.
That is one reason you should treat the TDEE result as a starting estimate rather than an exact daily calorie number.
Why Does the BMR Calculator Ask for Age?
Age is one of the inputs in the Mifflin St Jeor equation.
The formula includes age because resting energy expenditure tends to differ across age groups. The original Mifflin St Jeor research therefore included age as one of the variables used to predict resting energy expenditure.
You do not need to calculate this manually. Enter your current age and the calculator handles the calculation automatically.
If your age changes, the calculated result may change even if your height and weight remain the same.
Why Does Gender Matter in the Formula?
The Mifflin St Jeor equation uses different constants for men and women.
The male equation ends with plus 5, while the female equation ends with minus 161.
This does not mean every man or every woman has the same metabolic rate. It is simply part of the statistical equation developed from the research population.
Individual metabolism varies considerably, which is one reason a predictive equation should not be mistaken for a laboratory measurement.
How Accurate Is a BMR Calculator?
A BMR Calculator can provide a useful estimate, but no online equation can know your exact resting energy expenditure.
Research comparing commonly used predictive equations found that Mifflin St Jeor was more reliable than several other widely used equations and was more likely to estimate resting metabolic rate within 10 percent of measured values. However, the same review also noted important individual limitations.
That distinction is important.
A formula can perform well across a population while still being noticeably different from the measured value for one particular person.
Your result can be influenced by body composition, age, health status, and other factors that are not fully captured by a basic equation.
If a precise measurement of resting energy expenditure is clinically important, indirect calorimetry can be used in an appropriate professional setting.
What Can Affect Your Actual Metabolic Rate?
Your actual energy expenditure is more complicated than four numbers entered into a calculator.
Body Composition
Muscle and other metabolically active tissues contribute to energy expenditure. Two people with identical height, weight, age, and gender can still have different body compositions.
The original Mifflin St Jeor research found that fat free mass was an important predictor of resting energy expenditure.
Age
Age is included in the equation because resting energy expenditure tends to vary with age.
Body Weight
Weight is one of the major inputs in the Mifflin St Jeor equation.
Health Conditions
Certain health conditions can affect energy expenditure. A basic equation cannot fully account for every medical circumstance.
Medications and Other Factors
Some medications and physiological factors can influence energy needs. This is another reason a calculated number should not be treated as a personal medical prescription.
BMR and Weight Management
BMR is often used as the starting point for estimating calorie needs during weight management.
However, there is a common misunderstanding worth clearing up.
Your BMR is not your recommended calorie intake.
Eating exactly at your estimated BMR is not automatically appropriate for weight loss, maintenance, or weight gain.
Your body needs energy for more than resting functions. Your total energy needs depend on your daily activity and other components of energy expenditure.
The CalculatorKits tool therefore provides TDEE in addition to BMR.
If you want to explore estimated daily calorie requirements separately, you can use the CalculatorKits Calorie Calculator.
For a more detailed look at total daily energy expenditure, the TDEE Calculator can also be useful.
How the Fitness Goal Results Should Be Interpreted
The CalculatorKits tool includes goal options for weight loss, maintenance, and muscle gain.
It also displays estimated calorie differences associated with those goals.
These numbers should be treated as educational estimates rather than fixed instructions.
For example, a calculated calorie deficit does not guarantee a particular amount of weight change. Actual results vary from person to person and can change over time.
The tool also provides estimated timelines for losing or gaining a specified amount of weight. These are mathematical projections, not promises about what your body will do.
This distinction is especially important with nutrition. A calculator can provide a useful starting point, but individual circumstances may require professional guidance.
BMR Calculator vs Calorie Calculator
The two tools are closely related but have different purposes.
A BMR Calculator focuses first on estimated resting energy expenditure.
A Calorie Calculator is generally more focused on estimated daily calorie requirements after considering activity.
You can think of BMR as one part of the bigger energy picture.
If you are trying to understand how your resting estimate connects to your broader daily calorie needs, using both tools can make the relationship easier to understand.
BMR Calculator vs TDEE Calculator
BMR and TDEE should not be confused.
BMR describes resting energy expenditure.
TDEE estimates total daily energy expenditure.
The CalculatorKits BMR Calculator already calculates an estimated TDEE after you select your activity level, so you can see both figures together.
A dedicated TDEE Calculator can be useful when you specifically want to focus on total daily energy expenditure.
Can Body Fat Percentage Affect BMR?
Body composition can influence resting energy expenditure, but the standard Mifflin St Jeor equation does not require your body fat percentage.
It uses age, gender, height, and weight.
This makes the equation convenient because you do not need to know your body fat percentage before calculating BMR.
If you want additional body composition information, the CalculatorKits Body Fat Calculator estimates body fat percentage using circumference measurements.
You can also use the Lean Body Mass Calculator to explore estimated fat free mass.
These measurements provide different information and should not be treated as interchangeable.
Common BMR Calculator Mistakes
- Entering the wrong weight unit. Check whether the calculator is set to pounds or kilograms.
- Entering the wrong height. Make sure your height is entered in the format requested by the selected unit system.
- Selecting an unrealistic activity level. Do not choose Extra Active simply because you exercise occasionally.
- Confusing BMR with TDEE. Your resting estimate is not your complete daily calorie requirement.
- Treating the result as exact. Predictive equations have individual error.
- Changing activity levels without a real change in routine. This can create misleading TDEE estimates.
- Assuming a calorie target guarantees a particular result. Mathematical estimates cannot predict individual outcomes with certainty.
- Using the result as medical advice. A calculator is not a substitute for professional nutrition or healthcare guidance.
When Should You Recalculate Your BMR?
Your BMR estimate can change when your weight changes, and it also changes gradually as age changes.
The CalculatorKits tool suggests recalculating when weight or activity changes significantly or periodically while monitoring a nutrition plan.
There is no need to recalculate every day simply because your weight fluctuates slightly.
For practical tracking, meaningful changes in body weight, routine, or activity are more relevant than small day to day variations.
Who Should Be Careful With BMR Estimates?
General BMR equations are intended as estimates for adults.
Extra caution is appropriate when someone has a medical condition that affects metabolism, is pregnant or breastfeeding, has a complex nutritional situation, or requires medically supervised nutrition.
Athletes and people with unusual body composition may also find that a general predictive equation does not represent their individual energy expenditure particularly well. Research has shown that predictive equations can have meaningful individual errors, especially in populations that differ from the groups in which equations were developed or validated.
In these situations, professional guidance can provide a more appropriate interpretation.
Frequently Asked Questions
What is BMR?
BMR stands for Basal Metabolic Rate. It describes the estimated energy your body requires to maintain essential functions at rest.
What does a BMR Calculator calculate?
A BMR Calculator estimates resting energy expenditure using inputs such as age, gender, height, and weight. The CalculatorKits tool also estimates TDEE using your selected activity level.
What is the Mifflin St Jeor equation?
The Mifflin St Jeor equation is a predictive equation for resting energy expenditure. It was published in 1990 after researchers developed it from measurements of healthy adults.
Is BMR the same as TDEE?
No. BMR represents estimated energy expenditure at rest. TDEE is an estimate of total daily energy expenditure after activity is considered.
Is the BMR Calculator accurate?
It can provide a useful estimate, but it is not an exact measurement. Research supports Mifflin St Jeor as one of the better known predictive equations, while also showing that individual errors can occur.
Should I eat exactly my BMR calories?
Not necessarily. BMR is an estimate of resting energy expenditure, not a universal recommended calorie intake. Your total daily energy needs are higher than BMR for most people because daily movement and other activities require additional energy.
Does exercise increase BMR?
Exercise contributes to your overall energy expenditure, but it should not be confused with your calculated BMR. Your activity level is used separately when estimating TDEE.
Can BMR change when weight changes?
Yes. Weight is one of the main variables in the Mifflin St Jeor equation, so a meaningful change in weight can change the calculated estimate.
Can two people have the same BMR?
Yes. Two people can receive similar calculated BMR values even though their actual energy expenditure may differ because a simple equation cannot capture every individual difference.
Can I use this BMR Calculator for medical purposes?
No. The CalculatorKits tool is intended for general educational use. It should not replace personalized medical or nutrition advice.
Key Takeaways
A BMR Calculator estimates the calories your body uses at rest to support essential functions.
The CalculatorKits tool uses the Mifflin St Jeor equation.
Your BMR is not the same as your total daily calorie requirement.
Activity level is used to estimate TDEE from BMR.
The calculated result is an estimate, not a laboratory measurement.
Accurate age, height, weight, gender, and activity information can improve the usefulness of the calculation.
Mifflin St Jeor is one of the better studied predictive equations for resting energy expenditure, but individual differences still matter.
Do not treat a calculated calorie number as a guaranteed weight loss or weight gain outcome.
Use BMR as a starting point for understanding energy needs, not as a complete description of your metabolism.
Related CalculatorKits Tools
Calorie Calculator helps estimate daily calorie needs using activity and other information.
TDEE Calculator focuses specifically on estimated total daily energy expenditure.
Lean Body Mass Calculator provides an estimate of fat free body mass.
Body Fat Calculator estimates body fat percentage using body measurements.
References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990. PubMed reference
- Frankenfield D, Roth Y, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. Journal of the American Dietetic Association, 2005. PubMed systematic review
- Frankenfield D, Rowe WA, Smith JS, Cooney RN. Validation of several established equations for resting metabolic rate in obese and nonobese people. Journal of the American Dietetic Association, 2003. PubMed validation study
Medical Disclaimer
This calculator and the information in this article are provided for general knowledge and educational purposes only. The results are estimates and should not be considered medical or professional health advice. For personalized nutrition or health guidance, please consult a qualified healthcare professional.
Written and reviewed by the CalculatorKits Editorial Team
Last Updated: September 3, 2026