The Mifflin-St Jeor equation was published in 1990 by Mifflin, St Jeor and colleagues in the American Journal of Clinical Nutrition. They derived it from measurements of 498 healthy adults (247 women and 251 men) aged 19 to 78. In the same study, the 1919 Harris-Benedict equations overestimated measured resting energy expenditure by 5%. A 2005 systematic review in the Journal of the American Dietetic Association found Mifflin-St Jeor the most reliable of the common equations: it predicted resting metabolic rate within 10% of measured values in more nonobese and obese people than any other equation tested, though the authors noted meaningful errors for some individuals.
Formula
Men: REE = 10 × W + 6.25 × H − 5 × A + 5
Women: REE = 10 × W + 6.25 × H − 5 × A − 161
- REE: resting energy expenditure, kcal/day (used as an estimate of basal metabolic rate).
- W: body weight in kilograms.
- H: height in centimeters.
- A: age in years.
The paper's unrounded single equation is REE = 9.99W + 6.25H − 4.92A + 166 × sex − 161, with sex = 1 for men and 0 for women; the version above is the paper's simplified form.
Example
A 40-year-old man, 80 kg, 180 cm:
- 10 × 80 + 6.25 × 180 − 5 × 40 + 5 = 800 + 1,125 − 200 + 5 = 1,730 kcal/day
A 35-year-old woman, 68 kg, 165 cm:
- 680 + 1,031.25 − 175 − 161 ≈ 1,375 kcal/day
Multiplying the result by an activity level gives total daily energy expenditure. The BMR calculator and macro calculator both use this equation, and the guide to calculating macros applies it step by step.
Common mistakes
- Entering pounds and inches directly. Convert first: 1 lb ≈ 0.4536 kg and 1 in = 2.54 cm.
- Treating the result as exact. It was built on healthy adults and estimates a group average.