How this instrument works
Basal energy expenditure, BEE, estimates the calories a body burns at complete rest — the same quantity this site's own BMR calculator estimates with the newer Mifflin-St Jeor equation. This page instead runs the Harris-Benedict formula as revised by Roza and Shizgal in 1984: for men, 88.362 plus 13.397 times weight in kilograms, plus 4.799 times height in centimetres, minus 5.677 times age in years; for women, 447.593 plus 9.247 times weight, plus 3.098 times height, minus 4.330 times age.
The 1984 revision itself corrected the original 1919 Harris-Benedict equation, which J. Arthur Harris and Francis Benedict fitted from a much smaller, differently built early-twentieth-century study group. Roza and Shizgal re-derived the coefficients from a larger, more carefully measured sample and published the version this calculator uses, still widely cited as 'the' Harris-Benedict equation today even though it postdates the original by 65 years.
Set against Mifflin-St Jeor, the equation this site's BMR page uses, Harris-Benedict tends to run somewhat higher for the same body — a known, documented gap between the two methods, not an error in either one. A systematic review in the Journal of the American Dietetic Association found Mifflin-St Jeor the more accurate predictor for most healthy adults today, which is why current dietetic guidance generally favors it. Harris-Benedict remains useful here as the historical, still-common alternate reading, not a replacement for the newer figure.
- Set Sex — it selects which of the two independently fitted equations, men's or women's, runs.
- Enter Weight in kilograms, pounds, or stone.
- Enter Height in centimetres, metres, inches, or feet; internally the equation works in centimetres.
- Enter Age in years and read Basal energy expenditure (kcal/day), with every term of the sum shown.
Worked example — three BEE calculations
A 30-year-old man, 70 kg, 175 cm: weight term 13.397 × 70 = 937.79, height term 4.799 × 175 = 839.825, age term 5.677 × 30 = 170.31, subtracted. Add the men's constant of 88.362 and the sum closes at 88.362 + 937.79 + 839.825 − 170.31 = 1695.67 kcal per day.
A 30-year-old woman, 60 kg, 165 cm, runs through the separate women's equation: weight term 9.247 × 60 = 554.82, height term 3.098 × 165 = 511.17, age term 4.330 × 30 = 129.9, subtracted, plus the women's constant of 447.593: 447.593 + 554.82 + 511.17 − 129.9 = 1383.68 kcal per day.
A 50-year-old man, 90 kg, 180 cm: weight term 13.397 × 90 = 1205.73, height term 4.799 × 180 = 863.82, age term 5.677 × 50 = 283.85, subtracted, plus the men's constant of 88.362: 88.362 + 1205.73 + 863.82 − 283.85 = 1874.06 kcal per day — heavier weight pushes the number up, older age pulls it back down, and the two forces net out well above the 30-year-old case above.
Questions
Is BEE the same thing as the BMR figure on this site's Mifflin-St Jeor calculator?
They estimate the same underlying quantity, resting energy expenditure, but with different equations and different answers for the same body. Harris-Benedict, revised in 1984, is the older method and tends to read a little higher; Mifflin-St Jeor, from 1990, is the newer method most dietitians now treat as the more accurate default. Run both if you want to see the size of the gap for your own numbers.
Why does Harris-Benedict give a higher number than Mifflin-St Jeor for the same person?
Because the two equations were fitted to different study populations with different average body compositions, not because one contains an error. Roza and Shizgal's 1984 sample skewed toward a build that burned somewhat more at rest than Mifflin and St Jeor's 1990 sample did, and that difference carries straight through into the coefficients — a documented, consistent gap rather than a rounding artifact.
Which equation should I actually use, Harris-Benedict or Mifflin-St Jeor?
Mifflin-St Jeor for most people — a systematic review in the Journal of the American Dietetic Association rated it the more accurate of the common predictive equations for healthy nonobese and obese adults alike. Harris-Benedict remains in wide use for historical reasons and because many older clinical tools and references still quote it, which is exactly why this page exists: to run the older method honestly, not to present it as equally current.
What does BEE actually measure?
The energy a body would spend over 24 hours at complete physical and digestive rest — no food recently eaten, no exercise, lying still in a thermally neutral room. Almost nobody spends a real day meeting those conditions, so BEE functions as a floor: multiply it by an activity factor to estimate total daily energy needs, the same way this site's BMR calculator's output gets used.
Why do men and women get separate equations rather than one shared formula?
Because Roza and Shizgal fitted separate regressions for each sex, and the coefficients on weight, height, and age came out genuinely different between them, not just the constant term at the end. Men carry more lean mass on average at the same weight and height, and lean tissue burns more energy at rest, which is part of why the two equations diverge beyond a single offset.
Does a higher BEE number mean I should eat more calories?
Not directly — BEE is a resting floor, not a calorie target. Multiply it by an activity factor before comparing it to what you actually eat, and keep in mind that Harris-Benedict's tendency to read higher than Mifflin-St Jeor means building a diet plan around this figure alone can overshoot a genuine energy target by a meaningful margin for some people.
References
- Roza & Shizgal 1984, Am J Clin Nutr — Harris-Benedict reevaluated
- Frankenfield et al. 2005, J Am Diet Assoc — predictive equation review
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.