BMR calculator using the Mifflin–St Jeor equation
Enter adult age, equation sex, height and weight. HitEquals estimates resting calories, shows each equation term and compares the resting estimate with five activity scenarios.
Inputs used by this calculator
BMR Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Measurement system | US — inches and pounds | US — inches and pounds · Metric — cm and kg | Selects the unit or conversion path used by BMR Calculator. |
| Equation sex | Female equation | Female equation · Male equation | Supplies the equation sex quantity used by the published equation or result breakdown. |
| Age (years) | 35 | 20 to 100 | Supplies the age (years) quantity used by the published equation or result breakdown. |
| Height (inches or cm) | 65 | 36 to 275 | Supplies the height (inches or cm) quantity used by the published equation or result breakdown. |
| Weight (lb or kg) | 150 | 25 to 1000 | Supplies the weight (lb or kg) quantity used by the published equation or result breakdown. |
BMR and resting energy
Basal metabolic rate is the energy required under strict basal laboratory conditions. The Mifflin–St Jeor study predicted resting energy expenditure; consumer calculators commonly use it as a practical BMR estimate.
The result represents energy used before adding ordinary movement, work or exercise.
Mifflin–St Jeor formula
W is kilograms, H is centimeters and A is age in years. The published sex-specific constants create two versions.
men: 10W+6.25H−5A+5women: 10W+6.25H−5A−161Worked example
For a 35-year-old woman at 68 kg and 165 cm: 680 + 1,031.25 − 175 − 161 = 1,375.25 kcal/day. Rounding to a whole calorie gives 1,375.
BMR versus TDEE
BMR or RMR covers resting energy. Total daily energy expenditure adds activity and the energy costs of daily living. Use the TDEE Calculator when activity is part of the question.
Why estimates differ
Measured resting expenditure can differ because predictive equations summarize populations. Lean mass, illness, temperature, hormones, medication and measurement conditions can matter.
Using the number
Treat the estimate as a baseline for comparison. A food target requires an activity estimate and observation over time; clinical nutrition planning may require professional assessment.
Resting and total energy terms
| Term | Meaning |
|---|---|
| BMR | Strict basal energy |
| RMR | Resting energy under less restrictive conditions |
| TDEE | Resting energy plus daily activity |
| EER | Estimated intake to maintain energy balance |
Frequently asked questions
Is BMR the calories I should eat?
No. Food intake also needs to account for activity and individual goals.
Why does the equation ask for sex?
The published Mifflin–St Jeor equation uses different constants for its male and female groups.
Is BMR the same as TDEE?
No. TDEE adds activity to resting energy.
Can this measure metabolism exactly?
No. It is a prediction equation, not indirect calorimetry.
Does exercise change the BMR result?
Exercise is not an input to BMR; it is considered in TDEE.
What question does this BMR Calculator answer?
Estimate adult resting energy expenditure with the Mifflin–St Jeor equation.
What to keep in mind
This is an adult population estimate of resting energy expenditure. Individual metabolism, medical conditions, pregnancy, medication and measured laboratory results can differ.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.