The classic, widely referenced Harris-Benedict formula for estimating resting metabolic rate, using the revised 1984 coefficients.
How it works
Separate equations for men and women combine weight, height, and age, each with its own set of coefficients derived from body-composition research.
What this does not include
This does not include the newer Mifflin-St Jeor equation, which research has shown to be more accurate — this site’s separate daily calorie needs calculator uses that formula instead. This page exists for readers specifically looking for the named Harris-Benedict formula.
How to use this calculator
- Select your sex and enter your age, weight, and height.
A worked example
A 35-year-old man weighing 80 kg at 180 cm, using the revised 1984 male equation:
BMR = 88.362 + (13.397 × 80) + (4.799 × 180) − (5.677 × 35)
BMR = 88.362 + 1071.76 + 863.82 − 198.70 = 1,825 kcal/day
A 30-year-old woman weighing 65 kg at 165 cm, using the female equation:
BMR = 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 30) = 1,430 kcal/day
Both figures are resting expenditure only — the energy the body uses at complete rest, before any activity is added.
What the variables mean
| Variable | Meaning | Effect on the result |
|---|---|---|
| Weight | Body mass in kilograms | Largest single driver — each kg adds about 13.4 kcal for men, 9.2 for women |
| Height | Standing height in centimetres | Each cm adds about 4.8 kcal for men, 3.1 for women |
| Age | Age in years | Subtracts — roughly 5.7 kcal per year for men, 4.3 for women |
| Sex | Selects which coefficient set is used | Changes the constant and all three coefficients |
Edge cases worth knowing
The equation does not know your body composition. Weight enters as a single number, so two people of identical weight, height, age and sex return identical BMRs regardless of how much of that weight is muscle rather than fat — even though muscle is more metabolically active. This is the main reason individual results can differ from a measured value.
It was derived from, and fits best, a middle range. Harris-Benedict was built from a study population of generally healthy adults, and its accuracy falls off at the extremes of body size and at the ends of the age range.
BMR is not a calorie target. It is the resting baseline before activity, digestion and exercise are added — eating to your BMR is not the same as eating to maintain weight.
These figures are informational estimates from a population-level formula, not individual dietary advice; anyone making decisions about their own intake should speak to a qualified professional.
Frequently asked questions
Why does this site have two different BMR calculators?
The Harris-Benedict equation is older and specifically named in many textbooks and older diet plans; this site’s other calorie calculator uses the newer, more accurate Mifflin-St Jeor equation. Both are offered so readers can match whichever formula they specifically need.
Is Harris-Benedict less accurate than Mifflin-St Jeor?
Research has found Harris-Benedict tends to overestimate resting energy expenditure by about 5% compared to more modern measurements.
What year is this version of the equation from?
The coefficients used here are from a 1984 reevaluation of the original 1919 Harris-Benedict equation, the version most commonly cited today.
