Mifflin-St Jeor Equation (BMR)
The Mifflin-St Jeor equation calculates Basal Metabolic Rate (BMR) for men and women.
More accurate than Harris-Benedict for most people.
This page explains formulas involving personal body measurements. No data is collected or stored — all calculations shown are examples only.
The Formulas
The Mifflin-St Jeor equation estimates your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest, just to sustain basic functions like breathing, circulation, and cell repair. It was developed in 1990 by Mark D. Mifflin and Sachiko T. St Jeor and is now considered the most accurate predictive equation for most adults.
Variables
| Symbol | Meaning | Unit |
|---|---|---|
| BMR | Basal Metabolic Rate | kcal/day |
| weight_kg | Body weight in kilograms | kg |
| height_cm | Height in centimeters | cm |
| age | Age in years | years |
| +5 / −161 | Sex constant — +5 for men, −161 for women | kcal/day |
Example 1 — Adult Male
A 35-year-old man weighing 80 kg and 178 cm tall.
BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5
BMR = 800 + 1,112.5 − 175 + 5
BMR = 1,742.5 kcal/day — the minimum calories needed at rest.
Example 2 — Adult Female
A 28-year-old woman weighing 62 kg and 165 cm tall.
BMR = (10 × 62) + (6.25 × 165) − (5 × 28) − 161
BMR = 620 + 1,031.25 − 140 − 161
BMR = 1,350.25 kcal/day — the minimum calories needed at rest.
From BMR to Total Daily Calories (TDEE)
BMR is just your resting energy need. To find your Total Daily Energy Expenditure (TDEE), multiply BMR by an activity factor:
| Activity Level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | × 1.2 |
| Lightly active (light exercise 1–3 days/week) | × 1.375 |
| Moderately active (moderate exercise 3–5 days/week) | × 1.55 |
| Very active (hard exercise 6–7 days/week) | × 1.725 |
| Extremely active (physical job + daily training) | × 1.9 |
Why Mifflin-St Jeor is Preferred
- More accurate than the older Harris-Benedict equation (1919) for modern populations.
- Validated in multiple studies across diverse adult populations.
- Recommended by the Academy of Nutrition and Dietetics as the preferred predictive equation.
- Typically within 10% of measured BMR for most people with average body composition.
Limitations
- Less accurate for very muscular individuals — lean mass is not factored in.
- For athletes or those with unusually high or low body fat, the Katch-McArdle formula (which uses lean body mass) may be more appropriate.
- BMR is an estimate — actual metabolic rates vary due to genetics, hormones, and health conditions.