The Mifflin–St Jeor BMR Equation
Why dietitians use Mifflin–St Jeor instead of Harris–Benedict — and the exact formula, sourced from the original 1990 paper.
The formula
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
The single sex-specific constant at the end (+5 vs −161) reflects the average difference in lean mass between men and women at any given height and weight.
Where it comes from
Mark Mifflin and Sachiko St Jeor published the equation in 1990 after measuring resting metabolic rate via indirect calorimetry in 498 healthy adults aged 19–78, across a wide BMI range (17–42). The paper appeared in the American Journal of Clinical Nutrition and explicitly aimed to replace Harris–Benedict, whose 1919 dataset had skewed older and leaner than modern populations.
Accuracy
A 2005 systematic review by Frankenfield and colleagues compared four major BMR equations against measured resting metabolic rate in healthy adults. Mifflin–St Jeor was:
- The most accurate predictive equation overall.
- Within ±10% of measured BMR for 82% of non-obese adults.
- Within ±10% for 70% of obese adults — still the best performer for that group.
Harris–Benedict, by contrast, over-predicts BMR by ~5% on average in modern populations and is especially inaccurate for people with high body fat.
Worked example
A 35-year-old woman, 165 cm, 72 kg:
BMR = (10 × 72) + (6.25 × 165) − (5 × 35) − 161
= 720 + 1,031.25 − 175 − 161
≈ 1,415 calories/day
That’s her resting burn. Multiply by an activity multiplier to get her TDEE.
When to use a different equation
Mifflin–St Jeor uses total body weight — meaning a very muscular person will get an underestimate (lean mass burns more calories per kg than fat mass), and a person with very high body fat will get an overestimate.
If you have a reliable body-fat measurement from a DEXA or BodPod, use the Katch–McArdle formula instead:
BMR = 370 + (21.6 × lean body mass in kg)
For everyone else — including most people reading this — Mifflin–St Jeor is the right tool.
Try it
Use our TDEE calculator or maintenance calorie calculator — both are powered by the Mifflin–St Jeor equation.
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775–89.