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Estimates basal metabolic rate using the Mifflin-St Jeor equation.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
Basal metabolic rate is the energy required to sustain basic physiologic functions at rest and typically accounts for the largest share of total daily energy expenditure. The Mifflin-St Jeor equation estimates BMR in adults; total energy expenditure requires applying an activity factor. Estimates are approximate and should be used as a starting point for individualized nutrition assessment.
Specialty
Internal MedicineCategory
Internal MedicineDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-07
Formula
Keywords
Normal Range
Varies by age, sex, and body size
| Classification | Range |
|---|---|
Adult men | ~1,600–2,000 kcal/day |
Adult women | ~1,400–1,800 kcal/day |
Estimates basal metabolic rate (BMR) — the energy expended at complete rest — using the Mifflin-St Jeor equation with sex, age, weight, and height.
The Mifflin-St Jeor equation estimates BMR: males 10 x weight + 6.25 x height - 5 x age + 5; females 10 x weight + 6.25 x height - 5 x age - 161, with weight in kg, height in cm, and age in years.
Biological sex, which selects the male (+5) or female (-161) constant.
Age in years, multiplied by -5.
Weight in kilograms, multiplied by 10.
Height in centimeters, multiplied by 6.25.
The result is an estimate of the energy required at rest; typical adult estimates are roughly 1,600–2,000 kcal/day in men and 1,400–1,800 kcal/day in women, though values vary with age, body size, and body composition. Because there is no single 'normal' BMR, the calculator reports all valid results as normal. BMR is distinct from total daily energy expenditure, which also includes physical activity and the thermic effect of food.
Estimating BMR provides a foundation for nutritional assessment and energy-requirement planning in patients in whom resting energy expenditure cannot be measured directly.
A 40-year-old man weighing 70 kg with a height of 175 cm.
Inputs:
Expected Result: BMR = 10 × 70 + 6.25 × 175 − 5 × 40 + 5 ≈ 1598.8 kcal/day.
Weight must be entered in kilograms, height in centimeters, and age in years, matching the constants of the Mifflin-St Jeor equation. The sex selection matters because the equation applies a different constant for men than for women. Output is in kilocalories per day, so entering pounds or inches produces an estimate that does not correspond to the patient.
There is no single normal basal metabolic rate, because the estimate changes with age, sex, body size, and body composition, so every valid entry is reported as normal. For orientation, typical adult values fall roughly around 1,600-2,000 kcal/day in men and 1,400-1,800 kcal/day in women. Those figures are descriptive ranges rather than targets, and the result still requires individual clinical judgment.
Indirect calorimetry is preferred in critically ill patients, where a measured energy expenditure is available. The equation does not account for body composition, muscle mass, fever, illness, or other metabolic stress, so its estimate drifts from reality in those settings. The result also covers only rest: activity and the thermic effect of food must be added separately before it can inform a daily energy plan.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. BMR estimates are approximations and do not replace measured energy expenditure in patients whose nutritional support is clinically critical.