What is the most precise BMR formula?

November 24, 2025 •

3 min read

According to comparative studies, the Mifflin-St Jeor equation is the most accurate predictive formula for estimating basal metabolic rate (BMR) in a general population. This article explores why this formula outperforms others and explains the key factors influencing its precision.

Quick Summary

This guide compares BMR prediction equations like Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle, explaining which formula is generally considered the most precise for different populations and why.

Key Points

Mifflin-St Jeor is the most accurate formula for the general population: It uses modern data and accounts for factors like age, weight, and height more reliably than older equations.
Harris-Benedict is an older, less accurate alternative: While widely known, it tends to overestimate BMR in many modern individuals.
Katch-McArdle is better for lean individuals: This formula factors in lean body mass, making it superior for athletes or those with low body fat percentage.
All formulas are estimates, not perfect measurements: They provide a reliable starting point, but factors like genetics and hormones cause individual variance.
Indirect calorimetry is the most precise method overall: Clinical measurement in a lab setting is the gold standard for accuracy.
BMR changes based on age, diet, and activity: Metabolism naturally slows with age and can be affected by eating habits and muscle mass.

Understanding Basal Metabolic Rate (BMR)

Basal Metabolic Rate (BMR) represents the minimum number of calories your body needs to perform essential functions at complete rest. It constitutes a significant part of your daily energy use. While laboratory indirect calorimetry is the gold standard for accurate BMR measurement, it's often not practical for most people. Predictive equations offer a more accessible method using easily obtainable personal data.

The Mifflin-St Jeor Equation: The Modern Standard

The Mifflin-St Jeor equation, developed in 1990, is widely considered the most accurate formula for estimating BMR in today's general population. Its use of more recent data makes it a better fit for contemporary lifestyles compared to older formulas.

Mifflin-St Jeor Formulas:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Advantages:

Superior Accuracy: Research indicates it predicts BMR within 10% of measured values for a larger number of individuals, including those who are obese, when compared to the older Harris-Benedict equation.
Relevance: Based on modern data, providing a more appropriate estimate for current average body compositions.

The Classic: Harris-Benedict Equation

The Harris-Benedict equation was a long-standing standard for BMR calculation, first developed in 1919 and updated in 1984. While still used, it often overestimates BMR in modern individuals.

Revised Harris-Benedict Formulas:

Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)

The Alternative: Katch-McArdle Formula

The Katch-McArdle formula can offer a more accurate BMR estimate for very lean individuals who know their body fat percentage. This formula uses lean body mass (LBM) as a primary factor, which is a better indicator of metabolic rate than total weight for this group.

Katch-McArdle Formula:

For both sexes: RDEE (Resting Daily Energy Expenditure) = 370 + (21.6 × LBM in kg)

Comparison of BMR Formulas

Choosing the right BMR formula depends on individual characteristics. Here's a comparison to guide your decision:


Feature	Mifflin-St Jeor Equation	Harris-Benedict Equation	Katch-McArdle Formula
Development	1990	1919 (revised 1984)	N/A
Accuracy	Generally considered most accurate for the general population	Tends to overestimate in modern populations	More accurate for very lean individuals with known body fat percentage
Inputs Required	Weight, height, age, sex	Weight, height, age, sex	Lean Body Mass (LBM)
Best For	Most people seeking a reliable BMR estimate.	Historical context; less recommended for individual use.	Athletes, bodybuilders, or very lean individuals with body composition data.

The Limits of Predictive Equations

It's crucial to understand that predictive formulas provide estimates, not exact measurements. Factors like genetics, body composition, and hormone levels can cause individual variation in metabolic rate. Even the most precise formula, Mifflin-St Jeor, can have an error range.

Factors Influencing BMR Accuracy

Body Composition: Higher muscle mass correlates with a higher BMR. Formulas that don't directly account for LBM may be less accurate for individuals with extreme body compositions.
Genetics: Individual metabolic rates can be influenced by inherited factors not included in standard equations.
Hormones: Hormones, such as those from the thyroid, significantly regulate metabolism. Imbalances can affect the accuracy of a BMR calculation.
Dietary Habits: Restrictive dieting or fasting can lead to a decrease in BMR as the body attempts to conserve energy.

Conclusion: Which formula should you use?

For most individuals aiming to estimate calorie needs for weight management, the Mifflin-St Jeor equation is the most precise and dependable predictive formula. Its foundation on current population data makes it preferable to the older Harris-Benedict equation. However, for very lean individuals with access to body fat percentage data, such as athletes, the Katch-McArdle formula, which uses lean body mass, may offer a more accurate estimate. Regardless of the formula used, remember that the result is an estimate serving as a starting point for monitoring and adjusting based on personal results. Clinical indirect calorimetry remains the most accurate measurement method.

Taking the Next Step

To fully utilize your BMR, you need to consider your activity level. Multiplying your BMR by an activity factor yields your Total Daily Energy Expenditure (TDEE). Adjusting your caloric intake relative to your TDEE is essential for achieving weight goals. Online calculators often integrate these formulas for convenience. Consulting with a healthcare provider or registered dietitian is recommended for personalized guidance, particularly with health conditions or for elite athletes. For further information on metabolic health, authoritative resources like the National Academy of Sports Medicine are available.

Frequently Asked Questions

BMR (Basal Metabolic Rate) measures the minimum energy needed for vital bodily functions under strictly controlled, restful conditions, such as after a night's sleep and fasting. RMR (Resting Metabolic Rate) is a less restrictive measure of energy expenditure at rest, which also includes the energy used for digestion.

BMR calculators provide a good estimate but are not perfectly accurate. Even the most precise formula, Mifflin-St Jeor, can have an error margin of up to 10%. For most people, this is a sufficient and practical starting point for health and fitness goals.

Yes, BMR formulas are a key tool for weight loss. By calculating your BMR and adjusting for your activity level, you can determine your Total Daily Energy Expenditure (TDEE). Consuming fewer calories than your TDEE creates the calorie deficit necessary for weight loss.

Yes, muscle mass significantly impacts your BMR. Lean muscle tissue burns more calories at rest than fat tissue, meaning individuals with more muscle mass generally have a higher BMR. Resistance training is a recommended way to increase lean muscle mass and boost BMR.

While the Harris-Benedict equation is one of the oldest BMR formulas, its relevance is limited today, especially for individual use. It tends to overestimate BMR in modern populations and has been surpassed in accuracy by newer equations like Mifflin-St Jeor.

The Katch-McArdle formula is more accurate for very lean individuals because it is based on Lean Body Mass (LBM), which accounts for calorie-burning muscle tissue. Unlike formulas based on total weight, it bypasses the less metabolically active fat mass, leading to a more precise estimate for this specific demographic.

While many BMR factors like genetics and age are out of your control, you can increase your BMR by building lean muscle mass through strength and resistance training. Consuming enough calories and not engaging in extreme fasting can also prevent your body from slowing down its metabolism to conserve energy.