Understanding the Mifflin-St Jeor Equation

What is the Mifflin-St Jeor Equation?

The Mifflin-St Jeor equation is a formula used to calculate your BMR (Basal Metabolic Rate) — the number of calories your body burns at complete rest. It is the most widely used and recommended formula for the general population. It takes into account your total body weight, height, age, and gender.

BMR (male) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
BMR (female) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

It was developed in 1990 by Mark D. Mifflin and Susan T. St Jeor at the University of New Mexico, and it's considered the gold standard for estimating BMR in healthy individuals.

How is it different from Katch-McArdle?

The Katch-McArdle equation calculates BMR based on your Lean Body Mass (LBM), which requires knowing your body fat percentage.

BMR = 370 + (21.6 × Lean Body Mass in kg)

Key Difference: Mifflin-St Jeor estimates based on total weight, height, age, and gender, while Katch-McArdle calculates based on lean mass. This makes Katch-McArdle more accurate for individuals with known body composition, especially athletes.

Comparison with Other Equations

Equation	Based On	Accuracy	Best For
Mifflin-St Jeor	Weight, Height, Age, Gender	High (general population)	Most People
Katch-McArdle	Lean Body Mass	High (if body fat is known)	Athletes, Lean Individuals
Harris-Benedict (Revised)	Weight, Height, Age, Gender	Moderate	Older Adults
Cunningham	Lean Body Mass	High	Very Active Athletes

Why is Mifflin-St Jeor Recommended for Most People?

For the average person, body composition data (like body fat percentage) is often unavailable or difficult to measure accurately without specialized equipment. The Mifflin-St Jeor equation only requires common measurements: weight, height, age, and gender.

It provides a reliable estimate of BMR for the general population and serves as the starting point for calculating TDEE (Total Daily Energy Expenditure) by applying an activity multiplier.

When Should You Use Mifflin-St Jeor?

• If you are a healthy adult with average body composition.
• If you do not have access to accurate body fat percentage measurements.
• If you are looking for a widely accepted and validated formula.

Note: While highly accurate for the general population, individuals with very high muscle mass or very low body fat might find the Katch-McArdle equation more precise.