Mifflin-St Jeor Equation: The Science Behind Calorie Estimation

The Mifflin-St Jeor equation, published in 1990, is widely regarded as the most accurate formula for predicting Basal Metabolic Rate (BMR) in the general population. It is the equation used by the Academy of Nutrition and Dietetics and is built into Tooler's Calories Calculator.

The formulas: - Men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161... wait, that's women. Let me correct: - Men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5 - Women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161

Why Mifflin-St Jeor? Before this equation, the Harris-Benedict equation (1919) was the standard, but it overestimated BMR by about 5% in modern populations. The Mifflin-St Jeor equation was validated on a larger, more diverse sample and consistently produces more accurate estimates.

Accuracy: Research shows the Mifflin-St Jeor equation is accurate within approximately 10% for most individuals. However, it is still an estimate. Individual BMR can vary due to genetics, body composition (more muscle = higher BMR), hormonal factors, and medical conditions. The equation provides a starting point; adjust based on your actual results.

How Tooler uses it: The Calories Calculator computes your BMR with Mifflin-St Jeor, then multiplies by your selected activity level to estimate your TDEE. From there, it provides starting targets for maintenance, fat loss (TDEE − 500 kcal), and muscle gain (TDEE + 300 kcal).