Complete guide
BMR calculator using the Mifflin–St Jeor equation
Enter adult age, equation sex, height and weight. Calculator24 estimates resting calories, shows each equation term and compares the resting estimate with five activity scenarios.
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 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 display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.