BMR Calculator (Basal Metabolic Rate)

Enter your sex, age, height, and weight to calculate your Basal Metabolic Rate (BMR) — the minimum energy your body burns at rest — using both the original 1919 and revised 1984 Harris-Benedict equations, side by side.

Tips

  • BMR is the energy your body burns just to stay alive at complete rest — breathing, maintaining body temperature, and running your organs. It does not include any activity or exercise.
  • To estimate your total daily energy expenditure (TDEE), multiply this BMR value by an activity multiplier — roughly 1.2–1.375 for a mostly sedentary desk job, or 1.55 or higher if you exercise regularly.
  • It is normal for the two formulas to give slightly different numbers. The 1984 revision is based on newer body-composition data than the 1919 original, so it is usually considered closer to reality.
  • People with unusually high or low muscle mass (athletes, older adults) may find that this height/weight/age-based formula diverges noticeably from their actual BMR.

FAQ

BMR is the minimum amount of energy your body needs to stay alive — powering your heartbeat, breathing, and body temperature regulation without any physical activity. It typically accounts for about 60–70% of your total daily calorie burn.

It is a formula published in 1919 by American researchers James Arthur Harris and Francis Gano Benedict, which estimates BMR from sex, height, weight, and age. In 1984, Roza and Shizgal revised the coefficients using more current body-composition data.

Men generally carry more muscle mass and lower body fat than women, and muscle burns more energy at rest than fat does. So for the same height, weight, and age, men tend to have a higher BMR — the equations use separate coefficients to reflect this difference in body composition.

Eating well below your total daily energy expenditure (BMR adjusted for activity level) tends to produce weight loss, but cutting calories drastically below your BMR itself can risk muscle loss and a slowed metabolism, so extreme restriction is not recommended.
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Side Note — A formula born in a lab a century ago

The roots of the Harris-Benedict equation trace back, surprisingly, to 1919 — right after the end of World War I. At the Carnegie Institution in Washington, D.C., nutrition researchers James Arthur Harris and Francis Gano Benedict measured the respiratory gas exchange (indirect calorimetry) of hundreds of subjects, and statistically derived the relationship between height, weight, age, sex, and energy expenditure.

The formula remained the standard in nutrition and medicine for over six decades, until 1984, when researchers Anne Roza and Shakuntala Shizgal revisited the original coefficients using more current data and published a more accurate revised version. This tool displays both formulas side by side precisely to reflect that history.

In 1990, the Mifflin-St Jeor equation was published, considered a better fit for modern body types than Harris-Benedict, and it is increasingly used in clinical settings today. Even so, Harris-Benedict remains the most widely known BMR formula, and the fact that painstaking lab measurements from a century ago still underpin modern diet and nutrition tracking is one of the more fascinating stories in the history of nutrition science.

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