The Mifflin-St Jeor Formula Guide
If you've ever used a calorie or TDEE calculator, there's a good chance it relied on the Mifflin-St Jeor equation. Published in 1990, it has become the gold-standard formula for estimating Basal Metabolic Rate because it's more accurate for modern populations than older equations.
See how many calories you burn at complete rest.
The Equation
Mifflin-St Jeor estimates BMR in calories per day:
Men: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
The only difference between sexes is the constant at the end, reflecting average differences in body composition.
Worked Example
Take a 30-year-old woman, 165 cm tall, weighing 65 kg:
(10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031.25 − 150 − 161 = 1,370 calories/day.
That's her BMR. Multiply by an activity factor to get her TDEE, or just use our BMR calculator to skip the arithmetic.
See how many calories you burn at complete rest.
Mifflin-St Jeor vs Harris-Benedict
The older Harris-Benedict equation (1919, revised 1984) tends to overestimate BMR by around 5% for many people because it was based on a less representative sample. Mifflin-St Jeor was validated against more modern data and is now recommended by most dietitians as the default. Both are estimates, but Mifflin-St Jeor is the safer starting point.
Limitations
Like all formulas, Mifflin-St Jeor uses total body weight and can't see your body composition. Very muscular or very lean people may get more accurate results from the Katch-McArdle formula, which uses lean body mass. For most people, though, Mifflin-St Jeor is within a few percent of reality — close enough to set goals and refine from there.
Frequently Asked Questions
+Why is Mifflin-St Jeor preferred?
It was validated on a more representative modern population and is more accurate than the older Harris-Benedict equation for most people.
+Is Mifflin-St Jeor accurate?
It's typically within about 10% of measured BMR — excellent for a formula that needs only height, weight, age, and sex.
+When should I use Katch-McArdle instead?
If you know your body fat percentage and are very lean or muscular, Katch-McArdle (which uses lean mass) can be more accurate.
Conclusion
The Mifflin-St Jeor formula is the most reliable everyday method for estimating BMR. Use it as the foundation of your calorie plan, then refine your numbers based on real-world results over a few weeks.
See how many calories you burn at complete rest.