Harris-Benedict Energy Requirement Calculator
Harris-Benedict Energy Requirement Calculator
The 1919 original and the 1984 Roza-Shizgal revision are different equations with different numbers. This computes either, says which, shows the other alongside — and shows where the two cross.
Harris-Benedict basal energy expenditure
1919 original or 1984 revision1919 original. Male, 70 kg, 176 cm, 45 years
Both versions, in full
Men: BEE = 66.47 + 13.75 × weight (kg) + 5.003 × height (cm) − 6.755 × age (y)
Women: BEE = 655.1 + 9.563 × weight (kg) + 1.850 × height (cm) − 4.676 × age (y)
1984 Roza-Shizgal revision
Men: BEE = 88.362 + 13.397 × weight (kg) + 4.799 × height (cm) − 5.677 × age (y)
Women: BEE = 447.593 + 9.247 × weight (kg) + 3.098 × height (cm) − 4.330 × age (y)
- which one this page implements
- whichever the selector says, with the other printed underneath. That is why the selector exists: a “Harris-Benedict” figure with no version attached cannot be checked
- they cross
- neither version is uniformly higher. Across adult weights, heights and ages the sign of the difference changes, and the two agree almost exactly for a 70 kg, 170 cm, 50-year-old woman — 1,405.2 against 1,405.0 kcal/day. The largest gaps found were 75.2 kcal/day in men with the revision HIGHER and 67.7 kcal/day in women with it LOWER, so “the revision gives a higher number” is false as a general statement
- the height coefficient in women
- 1.850 in 1919 against 3.098 in 1984 — the coefficient that changed most, by a factor of 1.67. At 176 cm that is 220 kcal/day of difference, mostly offset by the intercept falling from 655.1 to 447.593. Mixing an intercept from one version with a slope from the other is a large error that looks small
- decimals, and BEE rather than RMR
- transcriptions of the 1919 equation differ in the decimals they carry — 13.7516 rather than 13.75, 655.0955 rather than 655.1; this page implements the rounded forms as printed in the source it read them in, and at the default patient the two spellings differ by under 0.2 kcal/day. Harris and Benedict also measured basal metabolism, a stricter condition than the resting metabolic rate most modern equations predict
Worked example
1919 original. Male, 70 kg, 176 cm, 45 years
66.47 + 13.75 × 70 + 5.003 × 176 − 6.755 × 45 = 66.47 + 962.50 + 880.53 − 303.98
= 1,605.5 kcal/day, which the page rounds to 1,606
The 1984 revision on the same patient: 88.362 + 937.79 + 844.62 − 255.47 = 1,615.3 kcal/day — 9.8 kcal/day higher, and the page prints both so the choice is visible
Mifflin-St Jeor on the same patient returns 1,580 kcal/day, 26 kcal/day below the 1919 figure, in the direction Mifflin's own paper reported when it found Harris-Benedict overestimating measured expenditure by 5%
Switch sex to female and 1919 gives 1,439.7 against the revision's 1,445.3 — but the two cross elsewhere in the female range, so the ordering is not a rule
Change to female, 150 kg, 145 cm, 18 years: 1919 gives 2,273.6 and 1984 2,205.9 — a 67.7 kcal/day gap in the opposite direction, and the largest female gap found anywhere in the adult range
Every coefficient, both versions, both sexes
| Term | 1919, men | 1984, men | 1919, women | 1984, women |
|---|---|---|---|---|
| Constant | 66.47 | 88.362 | 655.1 | 447.593 |
| × weight (kg) | 13.75 | 13.397 | 9.563 | 9.247 |
| × height (cm) | 5.003 | 4.799 | 1.850 | 3.098 |
| − × age (y) | 6.755 | 5.677 | 4.676 | 4.330 |
Where the two versions sit relative to each other
| Patient | 1919 (kcal/day) | 1984 (kcal/day) | 1984 minus 1919 |
|---|---|---|---|
| Male, 70 kg, 176 cm, 45 y | 1,605.5 | 1,615.3 | +9.8 |
| Female, 70 kg, 170 cm, 50 y | 1,405.2 | 1,405.0 | −0.2 |
| Female, 50 kg, 155 cm, 30 y | 1,279.7 | 1,260.2 | −19.5 |
| Male, 110 kg, 188 cm, 75 y | 2,012.9 | 2,038.5 | +25.6 |
| Male, 40 kg, 145 cm, 90 y | 734.0 | 809.2 | +75.2 |
| Female, 150 kg, 145 cm, 18 y | 2,273.6 | 2,205.9 | −67.7 |
Two equations, one name, and the reason to say which
Harris and Benedict published a biometric study of basal metabolism in 1919, and the regression equations in it have been in continuous clinical use ever since. In 1984 Roza and Shizgal re-derived them against body cell mass and published a different set of coefficients. Both sets are called “the Harris-Benedict equation”, both are implemented in widely used calculators, and a figure quoted without a version cannot be checked. That is the problem this page exists to solve: it computes whichever version is selected, labels it, and prints the other underneath.
What the two versions do not do is sit in a fixed order. For a 70 kg, 176 cm man of 45 the revision reads 9.8 kcal/day higher; for a 50 kg, 155 cm woman of 30 it reads 19.5 kcal/day lower; for a 70 kg, 170 cm woman of 50 the two agree to 0.2 kcal/day. The largest gaps found across adult weights, heights and ages were 75.2 kcal/day in men with the revision higher and 67.7 in women with it lower. The reason is in the coefficient table: the female height coefficient rose from 1.850 to 3.098 while the constant fell from 655.1 to 447.593, and those changes cancel near average height and diverge away from it. So mixing a constant from one version with a slope from the other produces an error of a couple of hundred kcal/day that looks perfectly reasonable.
Accuracy is why this is not the equation most guidance now prefers. In 130 non-hospitalised adults, Harris-Benedict was more than 10% away from measured resting metabolic rate in 33% of them against 22% for Mifflin-St Jeor; another test group put it within ±10% in about 65% of men and 57.5% of women, with a mean bias near 9%. Mifflin’s own paper found it overestimating by 5%. In critical illness it fares worse, and the Penn State equations were built because Harris-Benedict and its weight-adjusted variants performed badly there — one analysis of 202 ventilated patients found the weight-adjusted form accurate in 18% overall and 0% in one subgroup.
So this page is for reading somebody else’s Harris-Benedict number and knowing what it is, more than for generating a new one. Where a figure is needed and the patient is not ventilated, Mifflin-St Jeor is better validated; where expenditure matters and a metabolic cart is available, ESPEN recommends measuring it — see the Weir equation. This page computes a figure and prints the published targets beside it with the guideline each comes from. The prescription is the clinician’s, taken with the patient in front of them.
Frequently asked questions
Which Harris-Benedict equation should I use?
State which one you are using, whichever you choose: the 1919 original and the 1984 Roza-Shizgal revision have different coefficients in every term. Most calculators that say “Harris-Benedict” without qualifying it implement the 1984 revision. Where a predicted figure is needed in an adult who is not critically ill, Mifflin-St Jeor is better validated than either.
Is the 1984 revision always higher than the 1919 original?
No, and this is the commonest misstatement about them: the two cross. For a 70 kg, 176 cm man of 45 the revision reads 9.8 kcal/day higher; for a 50 kg, 155 cm woman of 30 it reads 19.5 lower; for a 70 kg, 170 cm woman of 50 they agree to 0.2 kcal/day. The largest gaps found were 75.2 kcal/day in men, with the revision higher, and 67.7 in women, with it lower.
How accurate is Harris-Benedict?
In 130 non-hospitalised adults it was more than 10% from measured in 33%, against 22% for Mifflin-St Jeor. Another test group reported it within ±10% in about 65% of men and 57.5% of women with a mean bias near 9%, and the 1984 revision’s published 95% confidence range is ±213 kcal/day in men and ±201 in women. In 202 ventilated critical care patients the weight-adjusted form was accurate in 18%.
What is the difference between BEE and RMR?
Harris and Benedict measured basal metabolism, under stricter conditions than the resting metabolic rate most modern equations predict. The two are commonly treated as interchangeable and are not quite the same quantity, which is a small extra source of disagreement when equations are compared.
Why do sources give slightly different Harris-Benedict coefficients?
Version, and decimals. 1919 against 1984 matters. Decimals do not: transcriptions carry 13.7516 or 13.75, 655.0955 or 655.1, and at the default patient the two spellings differ by under 0.2 kcal/day. This page implements the rounded forms as printed in the source it read them in.
Related calculators
References
- Revised Harris–Benedict Equation: New Human Resting Metabolic Rate Equation. Metabolites. 2023;13(2):189. The transcription this page implements for both the 1919 original and the 1984 Roza–Shizgal revision; reports Harris-Benedict within ± 10% of measured in about 65% of men and 57.5% of women.
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. 498 healthy adults aged 19–78, 264 of normal weight and 234 obese; R² = 0.71. Harris-Benedict overestimated measured REE by 5% in this cohort.
- Frankenfield DC, et al. Validation of several established equations for resting metabolic rate in obese and nonobese people. J Am Diet Assoc. 2003;103(9):1152–1159. In 130 adults with a BMI of 18.8 to 96.8, calculated RMR was more than 10% from measured in 22% using Mifflin-St Jeor, 33% using Harris-Benedict and 35% using Owen.
- Pardo E, Constantin JM. Indirect calorimetry in mechanically ventilated patients to assess nutritional targets. ICU Management & Practice. 2021;21(6):297–300. “This ratio is measured between 0.67 and 1.3 in humans. The ratio is close to 1 for carbohydrate metabolisation, 0.8 for protein and 0.7 for lipids.”
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/