Key takeaways
- Revised (1984) for men: 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age.
- Revised (1984) for women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age.
- It was built from 239 mostly young, lean adults in Boston more than a century ago.
- It tends to run 60 to 120 kcal above Mifflin-St Jeor for the same person.
On this page
- The two versions
- In pounds and inches
- The story behind it
- Worked example
- More examples next to Mifflin-St Jeor
- Why the two equations behave differently
- Harris-Benedict vs Mifflin-St Jeor
- From Harris-Benedict to TDEE
- Does the choice matter for weight loss?
- When to use Harris-Benedict
- Harris-Benedict in hospitals
- Limitations
- Harris-Benedict equation questions
The two versions
Original (Harris and Benedict, 1918) Men: 66.4730 + 13.7516 × weight (kg) + 5.0033 × height (cm) − 6.7550 × age Women: 655.0955 + 9.5634 × weight (kg) + 1.8496 × height (cm) − 4.6756 × age Revised (Roza and Shizgal, 1984) Men: 88.362 + 13.397 × weight (kg) + 4.799 × height (cm) − 5.677 × age Women: 447.593 + 9.247 × weight (kg) + 3.098 × height (cm) − 4.330 × age
Both give BMR in kcal a day. The two versions usually land within 10 to 20 kcal of each other, so in practice the choice between them matters little. When a calculator says “Harris-Benedict”, it almost always means the 1984 revision, as ours does.
In pounds and inches
Revised (1984) Men: 88.362 + 6.077 × weight (lb) + 12.189 × height (in) − 5.677 × age Women: 447.593 + 4.194 × weight (lb) + 7.869 × height (in) − 4.330 × age Original (1918) Men: 66.47 + 6.24 × weight (lb) + 12.71 × height (in) − 6.755 × age Women: 655.1 + 4.34 × weight (lb) + 4.70 × height (in) − 4.676 × age
The story behind it
In the early 1900s, the Carnegie Institution ran a nutrition laboratory in Boston that measured how much energy people used at rest. James Arthur Harris, a statistician, and Francis Gano Benedict, a physiologist, took measurements from 239 people, 136 men and 103 women, and used statistics to fit equations that could predict resting metabolism from simple body measures. They published their results in 1918 and in a longer report in 1919.
For most of the 20th century, theirs was the equation dietitians and doctors used. In 1984, Roza and Shizgal re-analysed the original data with more modern methods and published updated coefficients. Six years later, Mifflin-St Jeor arrived, built from a larger and more varied group of modern adults, and over the following decades it became the preferred choice.
Worked example
A 30-year-old man, 175 cm (5′9″) and 80 kg (176 lb):
Revised: 88.362 + (13.397 × 80) + (4.799 × 175) − (5.677 × 30) = 88.362 + 1,071.8 + 839.8 − 170.3 = 1,830 kcal Original: 66.473 + (13.7516 × 80) + (5.0033 × 175) − (6.755 × 30) = 1,840 kcal Mifflin-St Jeor for comparison: 1,749 kcal
A 35-year-old woman, 165 cm (5′5″) and 65 kg (143 lb):
Revised: 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 35) = 447.6 + 601.1 + 511.2 − 151.6 = 1,408 kcal Original: 1,418 kcal Mifflin-St Jeor for comparison: 1,345 kcal
In both cases Harris-Benedict is 60 to 90 kcal higher than Mifflin-St Jeor. Multiply by an activity factor of 1.55 and the gap becomes roughly 100 to 130 kcal of TDEE.
More examples next to Mifflin-St Jeor
| Person | Harris-Benedict (1984) | Mifflin-St Jeor | Difference |
|---|---|---|---|
| Man, 22, 185 cm (6′1″), 70 kg (154 lb) | 1,789 | 1,751 | +38 |
| Man, 30, 175 cm (5′9″), 80 kg (176 lb) | 1,830 | 1,749 | +81 |
| Man, 55, 170 cm (5′7″), 95 kg (209 lb) | 1,865 | 1,742 | +123 |
| Woman, 25, 160 cm (5′3″), 55 kg (121 lb) | 1,344 | 1,264 | +80 |
| Woman, 35, 165 cm (5′5″), 65 kg (143 lb) | 1,408 | 1,345 | +63 |
The gap is smallest for young, lean, tall people, who look most like the group Harris and Benedict measured, and largest for heavier, older people. That is consistent with the finding that Harris-Benedict overestimates for many of today’s adults.
Why the two equations behave differently
Look at the weight coefficients. In the revised Harris-Benedict equation, each kilo adds 13.4 kcal for men and 9.2 kcal for women; in Mifflin-St Jeor, it adds 10 kcal for both. So for heavier men, Harris-Benedict climbs faster. In practice, extra weight in today’s adults is often fat, which burns relatively little at rest, so a steeper weight term tends to overshoot.
Harris-Benedict also uses different age and height terms for men and women, while Mifflin-St Jeor uses the same ones and simply shifts the result with a sex constant. Neither approach is wrong; they are different fits to different groups of people.
Harris-Benedict vs Mifflin-St Jeor
| Harris-Benedict | Mifflin-St Jeor | |
|---|---|---|
| Published | 1918, revised 1984 | 1990 |
| Built from | 239 adults, mostly young and lean | 498 adults aged 19 to 78, including people with obesity |
| Inputs | Weight, height, age, sex | Weight, height, age, sex |
| Typical result | Slightly higher | Slightly lower |
| Accuracy in reviews | Less accurate; tends to overestimate | Most accurate of the common equations |
A 2005 systematic review for the American Dietetic Association compared these and other equations against measured resting metabolism in healthy adults with and without obesity. Mifflin-St Jeor predicted within 10% of the measured value for more people, and its errors were narrower. Harris-Benedict tended to overestimate, which makes sense given that today’s average adult carries more fat relative to muscle than the people measured in 1918.
From Harris-Benedict to TDEE
Like any BMR equation, Harris-Benedict is multiplied by an activity factor to estimate TDEE:
| Activity level | Factor | Man above (BMR 1,830) |
|---|---|---|
| Sedentary | 1.2 | 2,196 |
| Lightly active | 1.375 | 2,516 |
| Moderately active | 1.55 | 2,836 |
| Very active | 1.725 | 3,156 |
| Athlete | 1.9 | 3,476 |
These multipliers are often called the “Harris-Benedict factors”, but they weren’t part of Harris and Benedict’s 1918 work. They were added later as a practical rule of thumb and are now used with every BMR equation.
Does the choice matter for weight loss?
A little. Take the 35-year-old woman above, lightly active. With Harris-Benedict her TDEE is 1,408 × 1.375 = 1,936 kcal, and a 20% deficit gives a target of about 1,549 kcal. With Mifflin-St Jeor her TDEE is 1,850 kcal and her target about 1,480. The difference is about 70 kcal a day, or roughly a quarter of a kilo (half a pound) a month.
That is real but small, and smaller than the error in either estimate. If she picks the Harris-Benedict target and loses more slowly than planned, two or three weeks of weigh-ins will show it, and a 100 kcal adjustment fixes it. The equation is a starting point; the scale finishes the job.
When to use Harris-Benedict
- As a comparison. Seeing it next to Mifflin-St Jeor shows you the range a reasonable estimate can fall in. Our BMR calculator shows both.
- To match another tool. Some apps, older textbooks and gym programmes still use it. Using the same equation makes their numbers comparable.
- If your own data says it fits. If you have tracked your weight and food and your real TDEE matches Harris-Benedict better, use it. Data beats theory.
For everyone else, start with Mifflin-St Jeor. If you are lean and know your body fat, consider Katch-McArdle.
Harris-Benedict in hospitals
For decades, hospital dietitians used Harris-Benedict, often multiplied by “stress” or “injury” factors, to estimate the needs of patients. Today many clinical teams prefer measured resting metabolism where it is available, or equations developed for specific patient groups. Illness, surgery and medicines change energy needs in ways a healthy-adult equation can’t capture, which is another reason our calculators are for healthy adults only.
Limitations
- It can’t tell muscle from fat, like all weight-based equations.
- The original group was small by today’s standards and not very diverse.
- It tends to overestimate resting metabolism in many modern adults.
- It isn’t designed for children, pregnancy or medical conditions that affect metabolism.
Whichever equation you use, treat it as a starting point and check it against two to four weeks of weigh-ins.
Harris-Benedict equation questions
Which Harris-Benedict equation should I use, original or revised?
The revised 1984 version by Roza and Shizgal. It is the one most calculators use. The two usually differ by only 10 to 20 kcal, so the choice rarely matters.
Does Harris-Benedict give BMR or TDEE?
BMR. Multiply it by an activity factor (1.2 to 1.9) to estimate TDEE.
Is Harris-Benedict more accurate than Mifflin-St Jeor?
For most adults, no. Reviews have found Mifflin-St Jeor more accurate, with Harris-Benedict tending to overestimate. Harris-Benedict is still useful as a comparison.
Does Harris-Benedict use body fat?
No. It uses weight, height, age and sex. For a body-fat-based estimate, use Katch-McArdle or Cunningham.
How long should I test a Harris-Benedict estimate?
Two to four weeks of steady eating and daily weigh-ins. If your weekly average weight stays flat at the estimated maintenance, it fits you; if not, adjust by 100 to 200 kcal.
Is Harris-Benedict good for weight loss planning?
It works as a starting point, but because it tends to overestimate, a target based on it may produce slower loss than planned. Mifflin-St Jeor is usually the better start; either way, adjust from your weight trend.
Are the activity multipliers part of the Harris-Benedict equation?
No. Harris and Benedict only published resting metabolism equations. The 1.2 to 1.9 activity factors were added later as a rule of thumb and are used with every BMR equation.
Why do some calculators give a higher BMR than others?
Often because they use Harris-Benedict instead of Mifflin-St Jeor. Harris-Benedict usually gives 60 to 120 kcal more for the same person.
Sources
- Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370-373. doi.org/10.1073/pnas.4.12.370
- Harris JA, Benedict FG. A biometric study of basal metabolism in man. Washington DC: Carnegie Institution of Washington; 1919. Publication no. 279.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182. doi.org/10.1093/ajcn/40.1.168
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi.org/10.1093/ajcn/51.2.241
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789. pubmed.ncbi.nlm.nih.gov/15883556/