BMR Calculator
Use this BMR calculator to estimate how many calories your body may use each day at rest from your age, height, weight, and selected prediction equation.
BMR Calculator
The usual default. Fitted to 498 healthy adults aged 19–78.
Optional — fills in the Katch–McArdle comparison below.
Enter values above to see results
Health disclaimer: This is a predicted basal metabolic rate — the energy your body uses at complete rest, not a calorie target to eat to. It is a general estimate for informational purposes only, based on population-average equations, and is not medical or dietary advice. Individual needs vary with genetics, body composition, medical conditions and medication. Consult a qualified healthcare professional before changing your diet or activity, and do not use crash-level calorie targets.
Health disclaimer: This result is a general prediction for informational purposes only. It is not a prescribed calorie intake, medical diagnosis, or substitute for professional advice.
About This BMR Calculator
This BMR calculator estimates resting energy expenditure in calories and kilojoules per day. It uses your measurements in a published prediction equation rather than directly measuring your metabolism.
The result represents energy used for essential homeostatic processes under resting conditions. It does not include normal walking, work, household movement, planned exercise, or the energy used to process food.
How to Use the BMR Calculator
- Select metric or US customary units.
- Enter your age.
- Enter your height and weight.
- Select the equation category required by the formula.
- Choose which equation to use.
- Add a body-fat percentage — required for Katch–McArdle, optional otherwise.
- Click Calculate.
- Review the estimated calories per day, the kilojoules, and the formula used.
Enter current measurements and use the same unit system throughout the calculation.
What Is BMR?
Basal metabolic rate is an estimate of the energy the body uses while at rest to support basic homeostatic processes. It is normally expressed as kilocalories per day, commonly called calories per day.
BMR is not the same as the number of calories used during a full day. Total daily energy expenditure also includes activity-related expenditure and the thermic effect of food.
Strict controlled conditions are used when basal metabolism is measured. Online tools instead apply prediction equations to the information entered.
How Is BMR Calculated?
The default calculation uses the Mifflin–St Jeor equation, which was developed from measured resting-energy data from 498 healthy adults aged 19 to 78.
For the male equation category:
BMR = 10W + 6.25H − 5A + 5
For the female equation category:
BMR = 10W + 6.25H − 5A − 161
Where:
- W is weight in kilograms.
- H is height in centimeters.
- A is age in years.
The formulas produce a prediction, not a direct metabolic measurement.
Calculation Example
Suppose a 30-year-old adult uses the male equation category and enters:
Weight: 80 kg
Height: 180 cm
Age: 30 years
The calculation is:
BMR = (10 × 80) + (6.25 × 180) − (5 × 30) + 5
BMR = 800 + 1,125 − 150 + 5
Estimated BMR = 1,780 calories per day
This means the equation predicts approximately 1,780 calories of resting energy use per day. It does not mean the person should eat exactly 1,780 calories.
Other Formula Options
Revised Harris–Benedict
The revised Harris–Benedict equations use age, height, weight, and a sex-based formula category. Results may differ from Mifflin–St Jeor because the equations use different coefficients and source data. For the example above, this equation predicts about 1,854 calories per day rather than 1,780 — a difference of roughly 4%.
Katch–McArdle
Katch–McArdle estimates resting energy from lean body mass:
Resting Energy = 370 + (21.6 × Lean Body Mass in kg)
Lean body mass is estimated from weight and body-fat percentage. Because it reads body composition directly, this equation has no separate male and female forms. Body-fat measurements can vary a great deal by method, so this option should not automatically be described as more accurate.
Whichever equation is selected, the other two are shown beside the result. Seeing the spread between three respectable equations is a better guide to how precise a predicted BMR really is than any single number.
BMR vs RMR
BMR and resting metabolic rate are closely related, but their testing conditions may differ. Basal testing generally requires more restrictive preparation, while resting measurements may be performed under somewhat less restrictive conditions.
Online prediction tools often use the terms closely because they estimate resting energy from equations rather than conducting a laboratory measurement.
BMR vs TDEE
| BMR | TDEE |
|---|---|
| Estimates energy used at rest | Estimates energy used during a typical full day |
| Does not require an activity level | Includes an activity estimate |
| Excludes planned exercise | Includes movement and exercise estimates |
| Is not a maintenance-calorie target | Is often used to estimate maintenance calories |
Total daily energy expenditure includes resting energy, activity energy expenditure, and the thermic effect of food. Use the TDEE Calculator when activity-adjusted daily energy expenditure is the main goal.
Can BMR Be Used as a Calorie Target?
BMR should not automatically be treated as a daily eating target, a minimum safe intake, or a weight-loss prescription. Individual calorie and nutrient needs depend on activity, body composition, health, medication, pregnancy, breastfeeding, goals, and other factors.
A qualified healthcare professional or registered dietitian can interpret energy estimates in the context of an appropriate eating plan.
Why the Estimate May Differ From a Metabolic Test
Prediction equations may differ from measured resting energy because of:
- Body composition
- Age and hormonal factors
- Genetics
- Health conditions
- Medication
- Recent weight changes
- Measurement errors
- Differences between the equation population and the individual
Studies comparing prediction equations with indirect calorimetry show that accuracy can vary across populations and individuals. Indirect calorimetry estimates energy expenditure from respiratory gas exchange and is widely used as a reference method for measuring resting energy expenditure.
When to Recalculate
Consider recalculating after a meaningful change in:
- Body weight
- Body-fat percentage
- Age
- Health status
- Medication
- Pregnancy or breastfeeding status
Small day-to-day changes in weight usually do not require a new calculation.
Who Should Seek Professional Guidance?
Speak with an appropriate healthcare professional before using the result for diet or weight management if you:
- Are under 18
- Are pregnant or breastfeeding
- Have an eating-disorder history
- Have a thyroid, metabolic, kidney, digestive, or hormonal condition
- Take medication that affects appetite, metabolism, or body weight
- Are underweight
- Experience unexplained weight change, persistent fatigue, or other concerning symptoms
Related Calculators
- TDEE Calculator — resting energy adjusted for activity
- Calorie Deficit Calculator — a target intake for a chosen rate of loss
- Weight Loss Calculator — how long a goal weight would take
- Body Fat Calculator — the percentage Katch–McArdle needs
- BMI Calculator — weight relative to height
Start Calculating
Enter your age and measurements above, then use the BMR calculator to review your estimated resting energy expenditure and the equation used.
Medical and Nutritional Disclaimer
This tool and its results are provided for general informational and educational purposes only. The output is an estimate based on the information entered and the selected prediction equation. It may not reflect actual metabolism, body composition, health conditions, medication use, pregnancy, breastfeeding, or individual nutritional needs. The result is not medical, nutritional, or dietetic advice and should not be treated as a diagnosis, prescribed calorie intake, or guaranteed measure of energy expenditure. Consult a qualified healthcare professional before making major diet, exercise, or weight-management decisions.
Frequently Asked Questions
What does a BMR calculator estimate?
It predicts resting energy expenditure in calories per day from the measurements and formula selected. The same figure is also shown in kilojoules.
Is BMR the same as maintenance calories?
No. Maintenance calories include the energy used through movement, exercise, and other daily activity. Use the TDEE Calculator for an activity-adjusted figure.
Does exercise change the calculation?
Exercise is not a direct input for the resting estimate. Activity is considered when estimating total daily energy expenditure instead.
Which formula should I choose?
Mifflin–St Jeor is a practical default for many adults. The other two are shown beside it for comparison, but no prediction equation is exact for every person — they routinely differ by 100 calories or more for the same measurements.
Can body-fat percentage be included?
Yes. Katch–McArdle works from lean body mass and requires it. The other equations accept it too, which fills in the Katch–McArdle comparison without changing their own answer. The reliability of that result depends partly on the accuracy of the body-fat estimate.
Why do different tools give different results?
They may use different equations, rounding rules, unit conversions, or input assumptions. A tool that reports one figure without saying which equation produced it is hiding a choice, not removing it.
Should I eat my BMR?
No. BMR is not a daily eating target, a minimum safe intake, or a weight-loss prescription. Individual calorie needs depend on activity, body composition, health, medication, pregnancy, breastfeeding, and personal goals. Speak to a qualified healthcare professional or registered dietitian.