The Harris-Benedict equation is a historic milestone in nutrition science. Published in 1919 by J. Arthur Harris and Francis G. Benedict, it was the first widely accepted formula for estimating basal metabolic rate (BMR) from simple measurements: height, weight, age, and sex. For nearly seventy years it was the standard tool in clinical dietetics and research. Today it is mostly of historical interest, replaced by the more accurate Mifflin-St Jeor equation, but understanding Harris-Benedict helps you appreciate how far calorie science has come.
Historical context (1919)
In the early 1900s, scientists knew that people of different sizes burned different amounts of energy, but no one had a practical way to predict it. Harris and Benedict at the Carnegie Institution of Washington measured the oxygen consumption of 239 healthy adults — 136 men and 103 women — under strict resting conditions. From these measurements, they derived a regression equation that predicted BMR with reasonable accuracy for the era.
The study was groundbreaking. Before Harris-Benedict, clinicians had to use tables or rough estimates. The equation gave doctors, dietitians, and researchers a repeatable, math-based method to estimate energy needs. It quickly became the global standard and appeared in textbooks, hospital protocols, and military nutrition planning for decades.
Original Harris-Benedict formula (1919)
The original equations used pounds for weight, inches for height, and years for age:
| Sex | Original formula (imperial) |
|---|---|
| Men | BMR = 66.5 + 13.75 × weight(lbs) + 5.003 × height(in) − 6.775 × age |
| Women | BMR = 655.1 + 9.563 × weight(lbs) + 1.850 × height(in) − 4.676 × age |
Harris-Benedict formula in metric
Converted to metric units (kilograms and centimeters), the equations become:
| Sex | Metric formula |
|---|---|
| Men | BMR = 88.362 + 13.397 × weight(kg) + 4.796 × height(cm) − 5.677 × age |
| Women | BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age |
Revised Harris-Benedict (1984)
In 1984, Roza and Shizgal published a revised version of the Harris-Benedict equation. They re-analyzed the original data with modern statistical methods and updated the constants to improve accuracy. The revised equations are:
| Sex | Revised metric formula |
|---|---|
| Men | BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age |
| Women | BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age |
The changes are subtle — mostly rounding and minor constant adjustments — but they improved accuracy by a few percentage points. For a deep dive into the 1984 update, see our Harris-Benedict Revised guide.
Accuracy comparison with Mifflin-St Jeor
Modern studies consistently show that Mifflin-St Jeor outperforms Harris-Benedict:
| Equation | Accuracy vs measured | Typical error |
|---|---|---|
| Mifflin-St Jeor | ~85–90% | ±10–15% |
| Harris-Benedict (1919) | ~70–80% | ±15–25% |
| Revised Harris-Benedict (1984) | ~75–85% | ±12–20% |
The gap matters in practice. For a 30-year-old woman, 65 kg, 165 cm, Harris-Benedict predicts a BMR about 100 calories higher than Mifflin-St Jeor. Over a month, that adds up to 3,000 excess calories — roughly the amount in a pound of fat.
When Harris-Benedict might still be useful
Despite its age, Harris-Benedict is not useless:
- Historical research: older studies may report results using Harris-Benedict, so understanding it helps you interpret legacy data.
- Clinical settings: some hospitals and dietetics programs still teach it as a backup method.
- Very elderly populations: limited validation data for Mifflin-St Jeor in the very old (80+) means some clinicians prefer Harris-Benedict or revised Harris-Benedict for this group.
Harris-Benedict calculation example
For a 35-year-old woman, 165 cm, 70 kg, using the revised metric formula:
BMR = 447.593 + 9.247 × 70 + 3.098 × 165 - 4.330 × 35 BMR = 447.593 + 647.29 + 511.17 - 151.55 = 1,454.5 calories/day
The same inputs with Mifflin-St Jeor give 1,495 calories/day — a difference of about 40 calories. For heavier or taller individuals, the gap widens.
Should you use Harris-Benedict today?
For most people, no. Mifflin-St Jeor is more accurate and easier to remember. Our BMR calculator uses Mifflin-St Jeor exclusively, and our TDEE calculator builds on it with activity multipliers. If you need to interpret older research or follow a clinician's specific instruction, Harris-Benedict is still available, but treat it as a rough estimate rather than a precise number.
Links to related resources
- BMR equations compared — full comparison of all major formulas
- BMR calculator — uses the modern Mifflin-St Jeor formula
- TDEE calculator — finds maintenance calories with activity multipliers
- Harris-Benedict Revised — the 1984 update explained
- Harris-Benedict Calculator — step-by-step calculation tool
Sources and further reading
These independent, authoritative sources inform the methods used on this page.