Harris-Benedict BMR Calculator: Original 1919 vs Revised 1984

Compute your basal metabolic rate with both the original 1919 Harris-Benedict equation and the revised 1984 Roza-Shizgal equation — side by side, with the full step-by-step math, the history behind the revision, and a Mifflin-St Jeor comparison.

Educational tool — not medical advice

Scope boundary

This tool (#517) is a deep dive into the Harris-Benedict equations: the original 1919 vs the revised 1984 formula, their history, and how they compare with Mifflin-St Jeor.

Tool #516 (bmr-calculator) is the practical companion: Mifflin-St Jeor BMR plus daily TDEE planning. Tool #289 (tdee-calculator) goes further into activity levels, calorie goals, and macros. If you want the historical Harris-Benedict detail, stay here; if you want everyday calorie planning, go there.

Calculate both versions

Original 1919

– kcal/day

Harris & Benedict, Carnegie Institution, 1919.

Revised 1984

– kcal/day

Roza & Shizgal, Am J Clin Nutr, 1984.

Step-by-step breakdown

Term	Original 1919	Revised 1984

A brief history: 1919 → 1984

1919 — Harris & Benedict publish the original equation

J. Arthur Harris and Francis Gano Benedict publish “A Biometric Study of Basal Metabolism in Man” (Carnegie Institution of Washington, Publication No. 279), based on indirect-calorimetry measurements. The equations quickly become the clinical standard for estimating basal metabolic rate.

Mid-20th century — the standard spreads

The 1919 equations are adopted worldwide in nutrition, medicine, and dietetics, and remain the default BMR estimate for decades.

1984 — Roza & Shizgal reevaluate

Allan M. Roza and Harry M. Shizgal publish “The Harris Benedict equation reevaluated: resting energy expenditure and the body cell mass” (American Journal of Clinical Nutrition), deriving new coefficients from 239 subjects (103 men, 136 women). The revision raises the constant term but lowers the weight, height, and age multipliers — typically producing values a few percent lower than the 1919 original.

1990 — Mifflin-St Jeor enters

Mifflin et al. publish a new predictive equation that later validation studies find more accurate for healthy adults. It is shown here as a modern reference point.

How the coefficients changed

Coefficient	Men 1919	Men 1984	Women 1919	Women 1984
Constant	66.4730	88.362	655.0955	447.593
Weight (per kg)	13.7516	13.397	9.5634	9.247
Height (per cm)	5.0033	4.799	1.8496	3.098
Age (per year)	−6.7550	−5.677	−4.6756	−4.330

Notice the pattern: the 1984 revision raised the constant but reduced every multiplier — the net effect is a slightly lower estimate for most adults.

Three-way comparison: typical profiles

Profile	Original 1919	Revised 1984	Mifflin 1990	1919 vs 1984 Δ

All values in kcal/day, computed live by the same engine as the calculator above.

Related calculators

TDEE & Calorie Planner (#289) BMI Calculator

Frequently asked questions

What is the Harris-Benedict equation?

The Harris-Benedict equation is a formula for estimating basal metabolic rate (BMR) — the calories your body burns at rest. Published in 1919 by J. Arthur Harris and Francis G. Benedict, it uses weight, height, age, and sex: for men BMR = 66.4730 + 13.7516×weight(kg) + 5.0033×height(cm) − 6.7550×age, and for women BMR = 655.0955 + 9.5634×weight(kg) + 1.8496×height(cm) − 4.6756×age.

What is the difference between the original (1919) and revised (1984) Harris-Benedict equations?

The 1984 revision by Roza and Shizgal recalculated the coefficients using data from 239 subjects. The revised equations use a larger constant but smaller weight, height, and age coefficients. In practice, the revised equation typically gives slightly lower BMR values than the original — usually by around 1–5% depending on body size — correcting the original's tendency to overestimate.

Why was the Harris-Benedict equation revised?

The original 1919 equation was derived from measurements on a small, mostly young male sample from the early 1900s. By the 1980s, researchers found it tended to overestimate resting energy expenditure in modern populations. Roza and Shizgal (1984) re-analyzed newer data to produce coefficients that better match measured values.

Harris-Benedict vs Mifflin-St Jeor: which is more accurate?

The Mifflin-St Jeor equation (1990) is generally considered the most accurate for healthy, normal-weight adults in validation studies, and it is the default in many clinical guidelines. Harris-Benedict (especially the revised 1984 version) remains widely used and is often close. This calculator shows both so you can compare them for your own numbers.

How do I calculate BMR with the Harris-Benedict equation by hand?

Pick your sex, then multiply: weight in kilograms by the weight coefficient, height in centimeters by the height coefficient, and age in years by the age coefficient. Add the constant, the weight term, and the height term, then subtract the age term. Example (revised, man 80 kg / 180 cm / 35 y): 88.362 + 13.397×80 + 4.799×180 − 5.677×35 = 1,825 kcal/day.

Does the Harris-Benedict equation use pounds or kilograms?

The formulas expect metric units: weight in kilograms and height in centimeters. If you measure in pounds and inches, convert first: kilograms = pounds ÷ 2.20462, centimeters = inches × 2.54. This calculator does the conversion for you automatically when you select imperial units.

Why do the original and revised versions give different results?

Because every coefficient changed. The 1984 revision raised the constant term (66.4730 → 88.362 for men) but lowered the weight, height, and age multipliers, so the net effect varies with body size. For most adults the revised value lands a few percent below the original, but for very heavy or tall people the difference can be smaller — try the calculator to see both.

Is the Harris-Benedict equation accurate for athletes or obese individuals?

Accuracy drops at the extremes. Harris-Benedict can overestimate for obese individuals because it is linear in total body weight, and it may underestimate very muscular people. For lean-mass-based estimates, formulas like Katch-McArdle or Cunningham (which use body-fat percentage) are usually preferred.

What is the difference between BMR and TDEE?

BMR (basal metabolic rate) is the energy your body needs at complete rest. TDEE (total daily energy expenditure) adds everything else: activity, exercise, digestion, and daily movement. BMR is only the baseline — typically 60–75% of TDEE for sedentary people.

Is this Harris-Benedict calculator medical advice?

No. This calculator is an educational tool that shows how the historical formulas work and how they compare. It is not medical advice and cannot diagnose or treat any condition. If you need calorie or nutrition guidance for a health goal or medical condition, consult a doctor or registered dietitian.

Who published the original Harris-Benedict study?

J. Arthur Harris and Francis Gano Benedict published the original equations in 1919 in the Carnegie Institution of Washington monograph "A Biometric Study of Basal Metabolism in Man" (Publication No. 279), based on indirect calorimetry measurements.

What did Roza and Shizgal change in 1984?

In their paper "The Harris Benedict equation reevaluated: resting energy expenditure and the body cell mass" (American Journal of Clinical Nutrition, 1984), Allan M. Roza and Harry M. Shizgal derived new coefficients from 239 subjects (103 men, 136 women), producing the equations most calculators call "Harris-Benedict" today.

Can I use the Harris-Benedict equation for weight loss?

It is commonly used as a starting point: estimate BMR, multiply by an activity factor to get TDEE, then eat slightly below that to lose weight. But it is only an estimate — real-world results vary, and sustainable weight loss should be discussed with a qualified health professional.

Why are there separate equations for men and women?

Men and women differ on average in body composition — men typically carry more lean muscle mass, which burns more energy at rest. The sex-specific constants and coefficients capture that average difference; neither formula accounts for an individual's actual muscle mass.

Free tool by NRTechStudio

Harris-Benedict BMR Calculator: Original 1919 vs Revised 1984

Scope boundary

Calculate both versions

Original 1919

Revised 1984

Step-by-step breakdown

A brief history: 1919 → 1984

1919 — Harris & Benedict publish the original equation

Mid-20th century — the standard spreads

1984 — Roza & Shizgal reevaluate

1990 — Mifflin-St Jeor enters

How the coefficients changed

Three-way comparison: typical profiles

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Frequently asked questions

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