BMR Calculator
Estimate basal metabolic rate from age, sex, height, and weight, with several established prediction equations.
BMR formula and inputs
Mifflin-St Jeor is the demonstration default; other equations are available for comparison.
Prediction equations use sex-specific constants or coefficients.
Years, from 18 to 100. Use digits and a decimal point only.
Enter 50-250 cm, or the equivalent in total inches.
Enter 20-350 kg, or the equivalent in pounds.
Required only for Katch-McArdle; enter 2-70 without a percent sign.
Results
Estimated energy use at complete rest under standardized basal conditions.
Estimated BMR is 1,384 kilocalories per day using Mifflin-St Jeor.
How to use this BMR calculator
What this calculator does
This calculator estimates basal metabolic rate (BMR): the amount of energy your body would be expected to use over a day under basal, resting conditions. It is a prediction from body measurements, not a direct metabolic measurement and not a personalized calorie prescription. The default Mifflin-St Jeor equation was developed to predict resting energy expenditure in adults, and the original study is available through the PubMed record for the Mifflin-St Jeor equation. A measured value from indirect calorimetry can differ from any equation-based estimate.
When to use it
Use the estimate when you want a baseline for understanding daily energy needs, when comparing how established prediction equations respond to the same body measurements, when checking a calculation made elsewhere, or when preparing a discussion with a qualified nutrition or healthcare professional. BMR is only the resting component of total daily energy expenditure; ordinary movement, exercise, and digestion add energy use beyond this baseline.
How to calculate
- The calculator opens with a complete demonstration: Mifflin-St Jeor, female, age 31, height 168 cm, and weight 65 kg. The result and a validated Excel workbook are ready immediately.
- Choose a BMR formula. Keep Mifflin-St Jeor for the reference-style calculation, or select another established equation for comparison. Katch-McArdle reveals one additional input because it uses lean body mass derived from body-fat percentage.
- Use the fields shown for the selected equation, then replace Sex, Age, Height, and Weight where applicable with the values you want to evaluate. Inputs that the chosen formula does not use are hidden. Use the Height unit and Weight unit selectors to switch between metric and imperial entries; valid current values are converted when the unit changes.
- Read BMR (Basal metabolic rate) in kilocalories per day. The equation line underneath shows how the selected method applied to the current inputs.
- Select Download Excel to export the current inputs and calculated result to a real .xlsx workbook. Select Reset to clear the demonstration data. After Reset, the export is unavailable until a complete valid state is entered again.
Input guide
BMR formula is a required selection. Mifflin-St Jeor uses age, sex, height, and weight; Harris-Benedict and Revised Harris-Benedict use the same four inputs with different coefficients; Schofield uses age, sex, and weight; Katch-McArdle uses weight and estimated lean body mass. Changing the formula can change the estimate even when the measurements stay identical. Do not interpret a difference between formulas as a measured change in metabolism.
Sex is required for Mifflin-St Jeor, both Harris-Benedict variants, and Schofield because those equations use sex-specific constants or coefficients; it is hidden for Katch-McArdle. Choose the category that corresponds to the equation you are applying. Age is required for every supported formula except Katch-McArdle and accepts 18 to 100 years; the demonstration uses 31. Age generally lowers the Mifflin-St Jeor estimate as it increases while the other listed inputs stay fixed. Enter years as a plain number with a decimal point if needed; commas, scientific notation, and words are rejected.
Height is required for Mifflin-St Jeor and the Harris-Benedict variants. Enter 50-250 cm or the equivalent 19.69-98.43 inches; the demonstration uses 168 cm. Taller height increases those estimates when other inputs are fixed. Height unit is required and switches between cm and total inches. Do not enter a feet-and-inches expression such as 5'6" in the numeric field.
Weight is required for every supported equation. Enter 20-350 kg or the equivalent 44.09-771.62 lb; the demonstration uses 65 kg. Higher weight generally raises predicted BMR. Weight unit is required and converts a valid current value between kilograms and pounds. Avoid adding unit letters inside the number field. Body fat percentage is required only when Katch-McArdle is selected; enter 2-70 as a plain number, for example 25, without a percent sign. It determines estimated lean mass, so at the same body weight a higher body-fat percentage yields a lower Katch-McArdle estimate.
Output guide
BMR (Basal metabolic rate) is the calculator's primary output, displayed as kilocalories per day. It is an estimate from the selected prediction equation, not a minimum intake target and not total daily calorie expenditure. A higher value means the equation predicts greater resting energy use for the supplied measurements; a lower value means less. The summary pills repeat that same canonical BMR value, identify the active formula, and indicate whether the entered height and weight are currently metric, imperial, or mixed. The equation line is explanatory text generated from the same model and does not perform a separate calculation.
Worked example
With the opening demonstration values, Mifflin-St Jeor for a female uses 10 × 65 + 6.25 × 168 – 5 × 31 – 161. That is 650 + 1,050 – 155 – 161 = 1,384 kcal/day. The displayed result, summary pill, equation text, and Excel workbook all use this same calculation. For additional context, the NCBI Endotext table on estimating resting metabolic rate presents the Mifflin-St Jeor equation and its adult input units.
Understanding BMR estimates
Prediction equations are practical because they need only a few inputs, but they cannot capture every factor that changes resting energy expenditure. Body composition, genetics, recent energy balance, temperature, illness, medication, pregnancy, and measurement conditions can all matter. The Mifflin-St Jeor equation was derived from a group of healthy adults and has since been compared with other methods in later validation studies. A systematic review of resting metabolic rate equations found Mifflin-St Jeor comparatively reliable among evaluated equations while also emphasizing meaningful individual error.
BMR and resting metabolic rate are often discussed together, but laboratory protocols can differ. Strict basal measurement requires highly controlled resting conditions. For everyday planning, an equation-based result should be treated as a baseline estimate rather than a direct observation. If a precise energy requirement matters clinically, a healthcare professional can decide whether formal measurement or a more specific assessment is appropriate.