The Harris-Benedict Equation
The Harris-Benedict equation is the oldest widely-used formula for estimating Basal Metabolic Rate — first published in 1919 and revised in 1984. It still appears in textbooks, clinical settings, and countless calculators, which is exactly why it is worth knowing which version you are looking at and how it compares to the modern default, Mifflin-St Jeor.
The Revised Equation (1984 — Use This One)
Roza and Shizgal refitted the coefficients on a larger dataset in 1984. This is the version our BMR calculator uses, with weight in kg, height in cm, and age in years:
| Formula (kcal/day) | |
|---|---|
| Men | 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age |
| Women | 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age |
Example: a 30-year-old man, 80 kg, 180 cm → 88.362 + 13.397×80 + 4.799×180 − 5.677×30 ≈ 1,854 kcal/day.
The Original Equation (1919 — Historical)
James Harris and Francis Benedict derived the original from indirect-calorimetry measurements of 239 subjects:
| Formula (kcal/day) | |
|---|---|
| Men | 66.473 + 13.7516 × weight + 5.0033 × height − 6.755 × age |
| Women | 655.0955 + 9.5634 × weight + 1.8496 × height − 4.6756 × age |
Against modern measurements the original overestimates BMR by roughly 5% on average — a meaningful drift when a calorie plan is built on it. If a calculator or textbook cites Harris-Benedict without a year, it is usually this 1919 version.
Harris-Benedict vs Mifflin-St Jeor
Mifflin-St Jeor (1990) was developed precisely because Harris-Benedict was drifting from modern measurements. In comparative studies it predicts measured resting metabolic rate within 10% for more adults than either Harris-Benedict version, which is why it is the primary result in our calculator and the default recommendation in the BMR calculator guide. Harris-Benedict remains useful as a cross-check: when both formulas roughly agree, your estimate is solid. What neither formula includes is activity — converting BMR to a daily calorie figure is a separate step covered in the BMR vs TDEE guide.
Frequently Asked Questions
Is the Harris-Benedict equation still accurate?
The 1984 revision remains a reasonable estimator, but Mifflin-St Jeor predicts measured resting metabolic rate
more accurately for modern populations and is the preferred default.
What is the difference between the original and revised versions?
The 1919 original was derived from a small early-20th-century sample and runs about 5% high. Roza and Shizgal
refitted the coefficients in 1984 on a larger dataset, improving accuracy.
Does the Harris-Benedict equation include activity?
No. It estimates BMR only. The activity multipliers (1.2–1.9) are a separate step that converts BMR into
TDEE — see the
TDEE formula guide for how to choose one honestly.