The Harris-Benedict equation is more than a century old and is still one of the most widely recognised formulas in nutrition. James Arthur Harris and Francis Gano Benedict published it in 1919 after measuring the basal metabolism of 239 people at the Carnegie Institution’s Nutrition Laboratory in Boston. In 1984 Roza and Shizgal revised its coefficients using newer measurements. This calculator gives both versions, places the Mifflin-St Jeor equation alongside as a modern check, and multiplies by an activity level to get daily calories.
How to use the Harris-Benedict calculator
- Select sex and enter your age, height and weight.
- Choose an activity level for the daily calorie figures.
- Read the original and revised BMR. They usually differ by under 100 kcal.
- Compare with Mifflin-St Jeor, shown with the difference, to see how the older equation sits against the more recent one.
Harris-Benedict formulas
W in kilograms, H in centimetres, A in years; results in kcal per day.
Original (1919), women: 655.1 + 9.563 W + 1.850 H − 4.676 A
Revised (1984), men: 88.362 + 13.397 W + 4.799 H − 5.677 A
Revised (1984), women: 447.593 + 9.247 W + 3.098 H − 4.330 A
Daily calories = BMR × activity multiplier
| Activity level (IOM 2005) | PAL range | Multiplier used here |
|---|---|---|
| Sedentary | 1.0 – 1.39 | 1.2 |
| Low active | 1.4 – 1.59 | 1.5 |
| Active | 1.6 – 1.89 | 1.75 |
| Very active | 1.9 – 2.5 | 2.2 |
Sources: Harris JA, Benedict FG, A Biometric Study of Basal Metabolism in Man, Carnegie Institution of Washington, Publication 279, 1919; Roza AM, Shizgal HM, The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass, American Journal of Clinical Nutrition 1984;40:168–182; Mifflin MD et al., Am J Clin Nutr 1990;51:241–247.
Worked example
A 35-year-old man, 180 cm and 80 kg, low active.
- Original: 66.5 + 13.75 × 80 + 5.003 × 180 − 6.755 × 35 = 1,831 kcal
- Revised: 88.362 + 13.397 × 80 + 4.799 × 180 − 5.677 × 35 = 1,825 kcal
- Mifflin-St Jeor: 1,755 kcal, so the revised Harris-Benedict is 70 kcal higher.
- Daily calories at ×1.5: revised 2,738, original 2,746 kcal.
Three equations compared
Resting energy for a 35-year-old woman (165 cm) and man (178 cm) at three weights.
| Sex (age 35) | Weight | Original 1919 | Revised 1984 | Mifflin-St Jeor 1990 |
|---|---|---|---|---|
| Woman | 55 kg | 1,323 | 1,316 | 1,245 |
| Woman | 70 kg | 1,466 | 1,455 | 1,395 |
| Woman | 85 kg | 1,610 | 1,593 | 1,545 |
| Man | 55 kg | 1,477 | 1,481 | 1,492 |
| Man | 70 kg | 1,683 | 1,682 | 1,642 |
| Man | 85 kg | 1,889 | 1,883 | 1,792 |
Which equation to use
- For most adults, Mifflin-St Jeor. A 2005 systematic review (Frankenfield et al.) rated it the most accurate of those compared.
- Harris-Benedict is a useful cross-check. If it agrees within about 100 kcal, your estimate is likely stable.
- The original tends to run high. It was fitted to people measured a century ago, with different body composition and measurement methods.
- The revised version corrects part of that, but still tends to give slightly higher values than Mifflin in many people.
Practical notes
All three equations give averages for a group. Real resting rates differ because of lean mass, genetics, thyroid function and other factors, and a prediction can be 10 percent or more off for an individual. Use the number as a start, track your weight for a few weeks and adjust. For more on single equations see the Mifflin-St Jeor Calculator, RMR Calculator and BMR Calculator. For daily plans see the TDEE Calculator and Calorie Calculator.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian about your own needs.
Sources
- Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, 1919.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 1984;40:168–182.
- Frankenfield D, et al. J Am Diet Assoc 2005;105:775–789.
Frequently asked questions
What is the Harris-Benedict equation?
It is one of the oldest equations for predicting basal metabolic rate, published in 1919 by James Harris and Francis Benedict of the Carnegie Institution from measurements on 239 people. It estimates BMR from weight, height, age and sex.
What is the revised Harris-Benedict equation?
In 1984 Roza and Shizgal re-fitted the coefficients using modern indirect calorimetry data, correcting the tendency of the original to overestimate metabolism. The revised equation is the version most often used today.
Is Harris-Benedict still recommended?
It remains in widespread use, but a 2005 review for the Academy of Nutrition and Dietetics found Mifflin-St Jeor to be more accurate in modern adults, including those with obesity. Many clinicians therefore prefer Mifflin-St Jeor and treat Harris-Benedict as a comparison.
What are the traditional Harris-Benedict activity factors?
Calculators often use 1.2, 1.375, 1.55, 1.725 and 1.9 for sedentary to extra-active. Their origin is informal and they are not part of the 1919 paper, so this page uses the Physical Activity Level categories of the Institute of Medicine (2005) instead.
Why do the original and revised results differ?
Because they were fitted to different data. The original over-predicts by about 5 percent for modern populations; the revised lowers the intercepts and adjusts the weight and age terms. Differences are typically 10 to 100 kcal a day.