Is Harris-Benedict or Mifflin-St. Jeor More Accurate for Metabolic Rate?

January 10, 2026 •

4 min read

Millions of people rely on predictive equations to estimate their daily caloric needs for weight management, but which is more reliable? A 2005 systematic review by the American Dietetic Association found the Mifflin-St. Jeor equation to be the most reliable, predicting resting metabolic rate (RMR) more accurately for more individuals, including those with obesity, than the Harris-Benedict equation.

Quick Summary

This article compares the accuracy and methodology of the Mifflin-St. Jeor and Harris-Benedict equations for estimating metabolic rate, highlighting Mifflin-St. Jeor's superior reliability due to its modern data and better performance across different body types, including obese individuals.

Key Points

Mifflin-St. Jeor is More Accurate: Studies consistently show the Mifflin-St. Jeor equation provides a more reliable estimate of metabolic rate for most modern adults, including those with obesity.
Harris-Benedict Overestimates: The older Harris-Benedict formula, based on early 20th-century data, often significantly overestimates caloric needs for today's population.
Modern Data is Key: Mifflin-St. Jeor was developed using a larger, more diverse population sample from 1990, making it more applicable to contemporary lifestyles and body compositions.
Not a Replacement for Precision Measurement: Both equations are estimates. The most accurate method is indirect calorimetry, typically used in clinical settings.
Consider Body Composition: For very lean or muscular individuals, other formulas that account for lean body mass, like Katch-McArdle, may offer greater accuracy.
Individual Needs Vary: The equations provide a baseline. Factors like genetics, hormones, and health status mean personal monitoring and adjustment are necessary.

The Core of Calorie Calculation: What are Predictive Equations?

Before diving into the specifics of each formula, it's crucial to understand what they aim to do. Predictive equations are mathematical formulas used to estimate your Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR), which is the number of calories your body burns at rest to maintain vital functions like breathing, circulation, and temperature regulation. Since directly measuring metabolic rate through methods like indirect calorimetry is costly and complex, these equations provide a simple, accessible estimation based on readily available data: age, sex, weight, and height.

The Classic: A Deeper Look at the Harris-Benedict Equation

Developed by James Arthur Harris and Francis Gano Benedict between 1918 and 1919, the Harris-Benedict equation was groundbreaking for its time and remained the gold standard for decades. It was based on data from 239 individuals and provided a benchmark for comparing the metabolic rates of healthy people against those with diseases. Although revised in 1984 to improve accuracy, the formula's foundation remains rooted in early 20th-century data and body types.

Harris-Benedict Formula (Revised 1984)

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)

Limitations of the Harris-Benedict Equation

The primary issue with the Harris-Benedict equation today is that it tends to overestimate energy expenditure, particularly in the modern, often more sedentary population. Studies have shown it can overestimate caloric needs by 7–24%, a significant margin that can impact dieting or weight management goals. The population data used for its development does not align with contemporary body compositions and lifestyles, which is a major drawback.

The Modern Contender: A Deeper Look at the Mifflin-St. Jeor Equation

Introduced in 1990, the Mifflin-St. Jeor equation was developed using modern data on a larger, more diverse population, including individuals who were overweight and obese. This makes it more relevant and reliable for today's population. It is now widely recommended by dietitians and nutrition professionals as the preferred predictive equation for most people.

Mifflin-St. Jeor Formula

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

Advantages of the Mifflin-St. Jeor Equation

Research consistently shows the Mifflin-St. Jeor equation to be more accurate than the Harris-Benedict formula. It has a smaller margin of error and better predictive capability across a wider range of body masses, making it particularly superior for estimating the needs of obese individuals, where the Harris-Benedict equation often significantly overestimates.

Comparison Table: Harris-Benedict vs. Mifflin-St. Jeor


Feature	Harris-Benedict Equation	Mifflin-St. Jeor Equation
Year Developed	1919 (Revised 1984)	1990
Data Population	Smaller, early 20th-century cohort	Larger, more modern and diverse cohort, including obese individuals
Accuracy	Tends to overestimate, especially in modern populations (7-24% overestimation shown in some studies).	More reliable and accurate for most individuals, predicting RMR within 10% of measured values for a higher percentage of people.
Best For	Group-level estimations or historical comparisons.	Most modern adults for individual fitness and nutritional planning.
Limitations	Outdated population data, significant overestimation in obese individuals.	Still a prediction; individual metabolism can vary. Does not account for lean body mass.

Beyond the Equations: The Gold Standard and Other Considerations

While predictive equations are useful tools, it is important to remember their limitations. The most accurate way to measure metabolic rate is through indirect calorimetry, a method that analyzes gas exchange to determine energy expenditure. However, this method is typically reserved for clinical or research settings due to its cost and complexity.

Here are some other factors to consider when estimating your metabolic rate:

Body Composition: The Katch-McArdle formula, which requires an estimate of lean body mass, can be more accurate for individuals with a significantly higher or lower muscle mass than the average person. However, this requires more data, including body fat percentage.
Individual Variation: Genetics, hormone levels, and underlying health conditions can all influence an individual's metabolism, causing their actual caloric needs to deviate from any standard equation.
Activity Factor: The BMR/RMR result from both Mifflin-St. Jeor and Harris-Benedict must be multiplied by an activity factor to determine your total daily energy expenditure (TDEE). The Mifflin-St. Jeor equation's use of modern data makes it the superior starting point for this calculation. Here is a typical list of activity factors:
- Sedentary: Little to no exercise (TDEE = BMR × 1.2)
- Lightly Active: Light exercise/sports 1–3 days/week (TDEE = BMR × 1.375)
- Moderately Active: Moderate exercise/sports 3–5 days/week (TDEE = BMR × 1.55)
- Very Active: Hard exercise/sports 6–7 days a week (TDEE = BMR × 1.725)
- Extra Active: Very hard exercise/physical job or 2x training (TDEE = BMR × 1.9)

Conclusion

In the ongoing comparison of predictive metabolic rate equations, the Mifflin-St. Jeor formula consistently emerges as the more accurate and reliable choice for the vast majority of people today. While the Harris-Benedict equation holds historical significance, its reliance on outdated population data makes it less precise for modern body compositions and lifestyles, often overestimating caloric needs. For a more accurate baseline from which to plan your nutritional goals, especially for individuals with obesity, the Mifflin-St. Jeor equation is the superior tool. Regardless of the equation used, it should always be considered an estimation that requires individual monitoring and adjustment based on your specific health and fitness journey.

For additional context on research comparing predictive equations, consult the following resource: Comparison of predictive equations for resting metabolic rate in obese and non-obese adults: a systematic review.

Frequently Asked Questions

The Mifflin-St. Jeor equation is more accurate because it was developed more recently, in 1990, using a larger and more diverse population dataset that better reflects modern body compositions and lifestyles. The Harris-Benedict formula, developed in 1919, is based on outdated data and tends to overestimate caloric needs for many people today.

For individual weight loss planning, you should use the Mifflin-St. Jeor equation. Its superior accuracy in modern populations, particularly those who are overweight or obese, provides a more reliable estimate of your metabolic rate and caloric needs. Using an overestimated figure from Harris-Benedict could lead to slower progress than expected.

Both formulas use weight, height, age, and sex as inputs. However, the Mifflin-St. Jeor equation features more updated coefficients and a different constant for men and women, leading to a more precise estimation for the average contemporary adult.

The initial calculation from either formula gives you your Resting Metabolic Rate (RMR). To find your Total Daily Energy Expenditure (TDEE), you must multiply the RMR by an activity factor based on your lifestyle (e.g., sedentary, moderately active). This step is necessary regardless of which base formula you use.

While less accurate for individuals, the Harris-Benedict equation can still be useful for group-level predictions or in resource-limited settings where modern data may not be readily available for comparison. However, for most individual health and fitness applications, Mifflin-St. Jeor is preferred.

Neither the standard Harris-Benedict nor the Mifflin-St. Jeor equation explicitly uses body fat percentage in its calculation. They rely solely on weight, height, age, and sex. For a formula that does account for lean body mass, the Katch-McArdle formula is a better alternative, though it requires body fat percentage data.

The most precise method is indirect calorimetry, which is a clinical test that measures your oxygen consumption and carbon dioxide production. Since this is not widely accessible, the Mifflin-St. Jeor equation is the best estimation available for most people. Tracking your caloric intake and monitoring your weight change over time also allows you to make personalized adjustments to your estimated needs.