Estimate daily energy use at rest with Mifflin-St Jeor and revised Harris-Benedict. Add an optional body-fat estimate to compare the Cunningham fat-free-mass equation, then review units, formula differences and substituted calculation steps.
- Three published equations
- Metric and US units
- Formula-by-formula steps
- No data sent by the tool
BMR and Resting Energy Calculator
Choose a headline equation and enter adult measurements. The tool keeps each formula result separate. It does not apply an activity multiplier or turn the result into a calorie target.
Male coefficients, age 30, 175 cm and 75 kg
Resting-energy formula comparison
Selected: Mifflin-St JeorBars compare equation estimates for the same inputs. The spread is not a measured confidence interval or a calorie-intake range.
Formula results
| Equation | Estimate | Difference from selected | Substituted equation |
|---|---|---|---|
| Mifflin-St Jeor | 1,699 kcal/day | Selected equation | 10 × 75 + 6.25 × 175 − 5 × 30 + 5 |
| Revised Harris-Benedict | 1,763 kcal/day | +3.8% | 88.362 + 13.397 × 75 + 4.799 × 175 − 5.677 × 30 |
| Cunningham | 1,820 kcal/day | +7.1% | 500 + 22 × 60 kg fat-free mass |
Input and result details
| Measure | Value | Role |
|---|---|---|
| Published equation set | Male coefficients | Used by Mifflin and Harris-Benedict |
| Age | 30 years | Age term in two equations |
| Converted height | 175 cm | Height term in two equations |
| Converted weight | 75 kg | Weight term in all available equations |
| Body fat | 20% | Produces estimated fat-free mass of 60 kg |
| Available formula spread | 6.9% | Range divided by the formula average, not an error interval |
Calculation steps
- Use age 30 years, height 175 cm and weight 75 kg.
- Apply the male Mifflin-St Jeor equation: 10 × 75 + 6.25 × 175 − 5 × 30 + 5.
- Add the terms without early rounding: 750 + 1,093.75 − 150 + 5 = 1,698.75 kcal/day.
- Round the displayed estimate to 1,699 kcal/day.
- Convert energy units: 1,698.75 × 4.184 = 7,107.57 kJ/day.
Recent calculations
Results stay in this page session. Nothing is sent by this calculator.
How to Use This BMR Calculator
- Choose Mifflin-St Jeor, revised Harris-Benedict or Cunningham as the headline equation.
- Select the male or female coefficient set published for Mifflin and Harris-Benedict. Cunningham uses fat-free mass and ignores this selection.
- Enter adult age, height and weight. Choose metric or US units before typing measurements.
- Enter body-fat percentage if you want a Cunningham comparison. Leave it blank when you do not have a measured or estimated value.
- Select “Calculate BMR.” Review the headline estimate, formula comparison, converted inputs and calculation steps.
Do not copy someone else’s body-fat percentage to unlock the third formula. An inaccurate percentage creates an inaccurate fat-free-mass estimate. Comparing the two height-weight-age equations is more useful than adding a guessed body-composition input.
What Is Basal Metabolic Rate?
Basal metabolic rate, or BMR, is the energy the body uses to support essential functions while at complete rest. Those functions include breathing, circulation, temperature control, cell activity and organ function. Energy is commonly reported as kilocalories per day. Food labels often call one kilocalorie a “calorie.”
A true laboratory BMR measurement uses strict conditions. The person rests, fasts and avoids recent physical activity in a temperature-controlled setting. Many practical equations were developed from resting energy expenditure, or REE, measured under less restrictive conditions. For this reason, a number produced by an online “BMR calculator” is best read as a predicted resting-energy value, not a direct basal measurement.
BMR, RMR and TDEE Compared
| Measure | What it represents | What this page does |
|---|---|---|
| BMR | Energy used under strict basal conditions after rest and fasting. | Uses the common search term while clearly labelling equation results as estimates. |
| RMR or REE | Energy used at rest under practical measurement conditions. | Mifflin-St Jeor was developed to predict resting energy expenditure. |
| TDEE | Total daily energy expenditure, including rest, activity and food processing. | Not calculated here. No generic activity multiplier is applied. |
The terms BMR and RMR are often used interchangeably outside a laboratory. Their definitions and measurement conditions differ, but both describe energy use before normal daily activity is added. TDEE is a larger and more variable quantity.
BMR Formulas Used by This Calculator
All equations below return kilocalories per day. Weight is in kilograms, height is in centimetres and age is in completed years. W means weight, H means height, A means age and FFM means fat-free mass in kilograms.
Mifflin-St Jeor equation
This calculator uses the widely implemented rounded form of the Mifflin-St Jeor equation. It uses current body weight, height, age and one of two published coefficient sets.
Female set: BMR = 10W + 6.25H − 5A − 161
The 1990 study developed a new resting-energy equation from measured data in adults with and without obesity. Its participants were ages 19 to 78, about 146 to 201 cm tall, about 46 to 143 kg and mostly within BMI 17 to 42. Using the equation outside those reported ranges is an extrapolation. A later systematic review found Mifflin-St Jeor more reliable than several common alternatives across the reviewed adult samples, though no prediction equation matched every individual.
Revised Harris-Benedict equation
Roza and Shizgal reanalysed the Harris-Benedict data in 1984 and published revised coefficients. This tool uses the revised equations, not the original 1919 coefficients.
Female set: BMR = 447.593 + 9.247W + 3.098H − 4.330A
Cunningham equation
Cunningham’s 1980 reanalysis identified lean body mass as the main predictor and proposed the following estimate:
BMR = 500 + 22 × FFM
The equation needs a fat-free-mass estimate. This page derives FFM from entered weight and body-fat percentage. Tape methods, consumer scales, skinfolds and scans do not produce identical body-fat values, so input-method error carries into the result.
Worked BMR Example
Consider an adult using the male coefficient set, age 30, height 175 cm and weight 75 kg. The Mifflin-St Jeor calculation is:
The displayed estimate is 1,699 kcal/day. Revised Harris-Benedict gives about 1,763 kcal/day. If entered body fat is 20%, estimated fat-free mass is 75 × 0.80 = 60 kg, and Cunningham gives 500 + 22 × 60 = 1,820 kcal/day.
These three numbers do not form a recommended eating range. They show how different fitted models respond to the same measurements. The page keeps the formulas separate so you can identify the equation behind each result.
Why BMR Calculators Give Different Results
- Equations were fitted to different participant samples and measurement data.
- Some models use age, height and weight, while Cunningham uses estimated fat-free mass.
- Rounded coefficients and early rounding can shift the final displayed number.
- Pounds and inches must be converted correctly before a metric equation is used.
- Body composition, ethnicity, health status, hormones and individual metabolism are not fully represented by a short equation.
A 2005 review described prediction accuracy in terms of results falling within 10% of measured resting metabolic rate. Even the best-performing equation missed that window for a meaningful share of individuals. Treat a formula as a starting estimate, not a personal measurement.
Which BMR Formula Should You Use?
Mifflin-St Jeor is a practical default for non-critically ill adults when resting energy cannot be measured. Revised Harris-Benedict provides a useful comparison because it uses the same four inputs with different coefficients. Cunningham adds body composition, but only when the body-fat input is credible.
| Equation | Inputs | Best use on this page | Main limitation |
|---|---|---|---|
| Mifflin-St Jeor | Weight, height, age and coefficient set | Default adult resting-energy estimate | Population equation, not an individual measurement |
| Revised Harris-Benedict | Weight, height, age and coefficient set | Second adult equation for comparison | Different sample and fitted coefficients |
| Cunningham | Weight and body-fat percentage | Fat-free-mass-based comparison | Depends heavily on body-fat accuracy |
If a dietitian, clinician or research protocol names a specific method, use that method rather than choosing the most convenient or highest result.
Factors an Equation Does Not Fully Capture
Body composition
Fat-free tissues have different energy demands from fat tissue. Two adults with the same age, height and weight can have different measured resting expenditure. Mifflin and Harris-Benedict do not directly include body composition.
Health, medication and recovery
Fever, thyroid disease, injury, surgery, severe illness, some medicines and other clinical factors can change energy expenditure. Hospital nutrition assessment requires condition-specific professional judgment and often measured values.
Pregnancy, lactation and growth
Pregnancy, breastfeeding, childhood and adolescence involve energy needs outside the scope of this general adult tool. Do not use its result as a plan for these situations.
Adaptation and weight change
Body weight and energy expenditure can change over time. A result based on an old weight does not remain fixed. Weight loss, weight gain, prolonged energy restriction and changes in lean tissue can alter measured needs.
How to Improve Input Quality
- Measure height without shoes on a firm, level surface.
- Use a recent weight from a calibrated scale on a hard floor.
- Enter total inches correctly. Five feet ten inches equals 70 inches, not 5.10 feet.
- Use completed years for age and avoid rounding weight or height before entry.
- Only enter body-fat percentage from a method you understand. Record the method when tracking change.
- Compare repeated measurements under similar conditions rather than reacting to one decimal place.
Common BMR Calculator Mistakes
- Calling a predicted value a measured metabolic rate.
- Using the original Harris-Benedict label while applying revised coefficients, or mixing coefficients from two versions.
- Entering pounds into a kilogram field or inches into a centimetre field.
- Treating BMR as TDEE without accounting for actual movement and food processing.
- Using BMR as a minimum, maximum or prescribed calorie intake without professional context.
- Entering an assumed body-fat percentage and treating Cunningham as more accurate automatically.
- Applying a general adult formula during pregnancy, childhood or critical illness.
Calculation Method and Review Sources
The Mifflin-St Jeor model and its adult resting-energy context were reviewed against the 1990 Mifflin study record. The revised Harris-Benedict coefficients were checked against the 1984 Roza and Shizgal publication record. Cunningham’s fat-free-mass equation was checked against the 1980 reanalysis record.
Interpretation limits were reviewed against the systematic review of resting-metabolic-rate equations and the Academy of Nutrition and Dietetics evidence guidance. The calculator converts US measurements with 1 inch = 2.54 cm, 1 pound = 0.45359237 kg and 1 kcal = 4.184 kJ. It keeps full precision internally and rounds display values only.
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Frequently Asked Questions
What is BMR?
Basal metabolic rate is the energy the body uses to maintain essential functions under strict resting conditions. An online BMR calculator predicts this value from body measurements; it does not measure metabolism directly.
How do I calculate BMR?
Choose a published equation and use its required inputs. The common Mifflin-St Jeor form uses weight in kilograms, height in centimetres, age in years and a male or female coefficient set. This calculator converts US units before applying the equation.
What is the difference between BMR and RMR?
BMR is measured under stricter fasting, rest and environmental conditions. Resting metabolic rate or resting energy expenditure uses less restrictive conditions. Online tools often use "BMR" for search familiarity while estimating resting energy.
Which BMR formula is most accurate?
No equation is most accurate for every adult. Mifflin-St Jeor is a practical default for many non-critically ill adults, revised Harris-Benedict offers a comparison, and Cunningham depends on a credible body-fat estimate. Indirect calorimetry measures resting expenditure more directly.
Why do BMR calculators give different answers?
Equations use different study samples, variables and coefficients. Unit conversion, coefficient rounding and body-fat input error also affect results. The difference between formulas is not a recommended calorie-intake range.
Is my BMR how many calories I should eat?
No. BMR covers predicted energy use at rest. Daily needs also include movement, exercise and food processing, while health goals and medical needs require individual assessment. Do not treat BMR alone as a prescribed intake.
Does exercise change BMR?
Exercise raises total daily energy expenditure and may affect body composition over time. A BMR equation does not add workout calories or calculate TDEE. Its result changes only when one of its entered variables changes.
Can children or pregnant people use this calculator?
No. This general page is designed for adults and does not model growth, pregnancy or lactation. These situations need age- or condition-specific guidance from a qualified professional.
Why does the calculator ask for a male or female equation set?
Mifflin-St Jeor and revised Harris-Benedict were published with two sex-specific coefficient sets. The choice is a formula input, not a complete model of identity, hormones or body composition. Ask a qualified professional which method fits your situation when the choice is unclear.
How can I get a more accurate resting-energy value?
Use accurate current measurements and avoid guessing body-fat percentage. For a direct assessment, a qualified service can perform indirect calorimetry under a defined protocol. Even measured values need clinical context when illness or treatment affects energy needs.
Health and Calculation Disclaimer
This calculator provides an educational adult resting-energy estimate. It does not diagnose metabolic or thyroid conditions, measure your metabolism, prescribe calorie intake or replace a physician or registered dietitian. Do not use it for children, pregnancy, critical illness or eating-disorder treatment. Seek qualified guidance before making a major diet or health change.