Mifflin–St Jeor Equation
Resting metabolic rate from weight, height, age and sex. Since 1990 the default when body composition is unknown.
On these inputs the 4 equations spread over 73 kcal. That is expected — every formula is an estimate, not a measurement.
What it means
Basal metabolic rate is what your body spends at rest — breathing, circulation, organ work. It is not "how much you may eat": it is the baseline you add activity to in order to get maintenance calories.
Mifflin and St Jeor published the equation in 1990 from a sample of 498 people, as a replacement for the 1919 Harris–Benedict equation, which systematically overestimated expenditure in modern, less active populations.
Accurate for
Adults of ordinary build, BMI 18.5–30. Error is roughly ±10% for most people.
Off for
Athletes with high muscle mass, severe obesity, children and teens. There, formulas driven by body fat — Katch–McArdle — do better.
Run all the equations at once
The calculator returns a range across every BMR equation and shows where they agree — more honest than a single number.
Open the calorie calculatorMifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990;51(2):241–7.