Updated
Harris-Benedict equation: original and revised formulas, with examples
The Harris-Benedict equation estimates resting energy use from weight, height, age and sex. The 1984 revision, which this calculator runs, is 88.362 + 13.397 × weight (kg) + 4.799 × height (cm) − 5.677 × age for men. The original dates from 1919. The revision is precise to about 14% in normally nourished adults.
These are example numbers. Enter your own above.
Your maintenance calories, as a range across equations
Each equation's BMR × 1.2 for your activity level. Mean of the equations 2,157 kcal/day, and the equations disagree by 90 kcal.
Your activity choice moves this estimate more than the equations disagree. One step to “Lightly active” moves the mean about 314 kcal/day, while the equations on your row span 90 kcal/day.
Is exercise already included? Yes. The “Sedentary” multiplier (×1.2) already covers your workouts and daily movement. Do not add calories burned in the gym on top of this number. Double-counting exercise is the most common reason these estimates come out too high.
| Mifflin-St Jeor | 2,112 kcal |
|---|---|
| Revised Harris-Benedict | 2,202 kcal |
| Katch-McArdle | add body fat % to include it |
| Activity level | Factor | Maintenance |
|---|---|---|
| Sedentaryselected | ×1.2 | 2,112–2,202 kcal |
| Lightly active | ×1.375 | 2,420–2,523 kcal |
| Moderately active | ×1.55 | 2,728–2,844 kcal |
| Very active | ×1.725 | 3,036–3,165 kcal |
| Extra active | ×1.9 | 3,344–3,486 kcal |
Show the work
Each equation estimates your basal metabolic rate (BMR), the energy you use at complete rest, from your sex, age, height and weight. Katch-McArdle instead uses lean body mass, which is why it needs a body fat percentage. Every BMR is then multiplied by your activity factor (×1.2) to reach maintenance calories. The range you see is the spread between equations, not a margin of error for your body.
Your weight, height, age, sex and body fat stay in this browser, on this device. Nothing is uploaded, there is no account, and no other company receives any of it. The button below deletes what this page stored, where this browser allows it.
Supported inputs: ages 18–80; height 130–230 cm (4 ft 3 in – 7 ft 7 in); weight 35–250 kg (77–551 lb); body fat 8–55% or blank. Imperial figures are rounded; metric limits are exact. Results are shown in whole calories per day.
What is the Harris-Benedict equation?
The Harris-Benedict equation predicts resting energy use from weight, height, age and sex. J. Arthur Harris and Francis G. Benedict derived the original equations at the Carnegie Institution of Washington from 239 adults: 136 men and 103 women. Their work appeared in a 1918 journal communication and the 1919 monograph A Biometric Study of Basal Metabolism in Man (Harris and Benedict, 1919).
The 1984 revision is subtitled "resting energy requirements" (Roza and Shizgal, 1984). It predicts resting energy. Calculators, this one included, label the result BMR by convention.
The equations were revised in 1984 and again in 2023 (Pavlidou and colleagues, 2023). Each version uses different coefficients, which is worth knowing when two calculators disagree.
The Harris-Benedict equation for men and women
The Harris-Benedict formula has separate equations for men and women. Weight is entered in kilograms, height in centimeters and age in years.
Original Harris-Benedict equation (1919)
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
These coefficients come from the original monograph's equations for 136 men and 103 women. Rounded forms such as 66.5 / 13.75 / 5.003 / 6.755 and 655.1 / 9.563 / 1.850 / 4.676 are common online and give results within a few kcal.
Revised Harris-Benedict equation (1984): the version this calculator uses
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
These are the coefficients this calculator uses. Roza and Shizgal refit the original data plus 98 later subjects, for 337 in total. The coefficients are also reproduced in the comparison table from the 2023 revision paper (Pavlidou and colleagues, 2023).
How to tell which version a calculator uses
Look at the constant. About 66 for men or 655 for women means the original. A constant of 88.362 for men or 447.593 for women means the 1984 revision.
The 2023 revision uses different constants, 260 for men and 43 for women, and uses height in metres. Its full formula is not printed here because this calculator runs the 1984 revision; see the History section below.
Table 1: all versions side by side
| Sex | 1919 original | 1984 revision | 2023 note |
|---|---|---|---|
| Men | 66.4730 + 13.7516 × weight (kg) + 5.0033 × height (cm) − 6.7550 × age | 88.362 + 13.397 × weight (kg) + 4.799 × height (cm) − 5.677 × age | Constant 260; height in metres |
| Women | 655.0955 + 9.5634 × weight (kg) + 1.8496 × height (cm) − 4.6756 × age | 447.593 + 9.247 × weight (kg) + 3.098 × height (cm) − 4.330 × age | Constant 43; height in metres |
How to calculate BMR with the Harris-Benedict equation
To apply the revised Harris-Benedict equation, convert body weight from pounds to kilograms and height from feet and inches to centimeters. Substitute the metric values into the equation for the person's sex. Add the constant and the positive terms, then subtract the age term. The result is an estimate of resting energy use in kcal per day.
The maintenance calorie calculator uses the 1984 revision. The examples below show how the original and revised equations produce slightly different results for the same body.
Worked example: a 30-year-old man, 5 ft 10 in, 175 lb
This body is 79.38 kg and 177.8 cm. Using the revised equation:
88.362 + (13.397 × 79.38) + (4.799 × 177.8) − (5.677 × 30) = 88.362 + 1,063.4 + 853.3 − 170.3 = 1,835 kcal/day
Using the original equation:
66.473 + (13.7516 × 79.38) + (5.0033 × 177.8) − (6.7550 × 30) = 66.473 + 1,091.6 + 889.6 − 202.7 = 1,845 kcal/day
Worked example: a 30-year-old woman, 5 ft 5 in, 140 lb
This body is 63.50 kg and 165.1 cm. Using the revised equation:
447.593 + (9.247 × 63.50) + (3.098 × 165.1) − (4.330 × 30) = 447.593 + 587.2 + 511.5 − 129.9 = 1,416 kcal/day
Using the original equation:
1,428 kcal/day
Table 2: step by step
| Body | Inputs in metric units | 1919 original | 1984 revision |
|---|---|---|---|
| Man, 30, 5 ft 10 in, 175 lb | 79.38 kg, 177.8 cm | 66.473 + 1,091.6 + 889.6 − 202.7 = 1,845 kcal/day | 88.362 + 1,063.4 + 853.3 − 170.3 = 1,835 kcal/day |
| Woman, 30, 5 ft 5 in, 140 lb | 63.50 kg, 165.1 cm | 1,428 kcal/day | 447.593 + 587.2 + 511.5 − 129.9 = 1,416 kcal/day |
For these two bodies, the original and revised equations differ by 10-11 kcal.
From BMR to daily calories: the activity factor
The Harris-Benedict result estimates resting energy. An activity factor is then multiplied by that result to produce a daily estimate that includes movement. The factor is a convention associated with the Harris-Benedict tradition, not the product of a validation study. A search of the primary literature found no source for the individual values.
The factor is a single decimal, typically ranging from 1.2 for little or no activity to 1.9 for intense daily exercise. Using the man's revised BMR of 1,835 kcal/day:
Table 3: the man's revised 1,835 kcal BMR across the five factors
| Factor | Level | Daily estimate |
|---|---|---|
| 1.2 | Sedentary | 2,202 |
| 1.375 | Lightly active | 2,523 |
| 1.55 | Moderately active | 2,844 |
| 1.725 | Very active | 3,165 |
| 1.9 | Extra active | 3,486 |
The multiplication is 1,835 × each factor. The displayed daily estimates are rounded to whole kcal. The activity level changes the result by hundreds of kcal, while the two Harris-Benedict versions differ by 10-11 kcal in the examples above.
History of the Harris-Benedict equation
The equation has two birth dates. December 1918 is the journal communication and 1919 is the full monograph, and both appear in the literature.
Table 4: timeline
| Year | Event | Source |
|---|---|---|
| Dec 1918 | Harris and Benedict, "A Biometric Study of Human Basal Metabolism", PNAS 4(12):370-373 | Harris and Benedict, 1918 |
| 1919 | Full monograph, Carnegie Institution Publication 279: equations from 136 men and 103 women | Harris and Benedict, 1919 |
| 1984 | Roza and Shizgal refit with 98 additional subjects, 337 total; report precision of ±14% in normally nourished adults, unreliable in malnourished patients | Roza and Shizgal, 1984, Pavlidou and colleagues, 2023 |
| 1990 | Mifflin and colleagues find the 1919 equations overestimate measured resting energy by 5% in 498 adults | Mifflin and colleagues, 1990 |
| 2023 | Pavlidou and colleagues publish new resting-rate equations from 722 adults, reported as more accurate than Harris-Benedict and Mifflin-St Jeor in their test group | Pavlidou and colleagues, 2023 |
How accurate is the Harris-Benedict equation?
Accuracy depends on the population and the comparison method. Roza and Shizgal reported a precision of ±14% in normally nourished adults. They also found the equations unreliable in malnourished patients, where they underestimated measured oxygen consumption (Roza and Shizgal, 1984).
Mifflin and colleagues tested the 1919 equations against measured resting energy expenditure in 498 adults. The equations overestimated by 5%, a difference that was significant at p < 0.01 (Mifflin and colleagues, 1990).
In obese adults, the Academy of Nutrition and Dietetics reports that Harris-Benedict with actual body weight was within 10% of measured resting metabolic rate in 39-64% of cases. Up to 43% of estimates were above the measured value, and up to 35% were below it. The corresponding figure for Mifflin-St Jeor was 70% (Academy of Nutrition and Dietetics).
These figures describe groups, not a guaranteed range for any one person.
Harris-Benedict vs Mifflin-St Jeor
For the two example bodies in Table 5, the original and revised Harris-Benedict equations produce results that differ by only 10-11 kcal. Mifflin-St Jeor comes in 60-85 kcal below the Harris-Benedict values for these same bodies, whichever version is used. That 60-85 kcal gap is modest compared with the effect of the activity factor, which changes a daily estimate by hundreds of kcal as movement level changes. In practice, the factor changes the final number far more than the choice of basal equation.
Table 5
| Body | Original HB (1919) | Revised HB (1984) | Mifflin-St Jeor |
|---|---|---|---|
| Man, 30, 5 ft 10 in, 175 lb | 1,845 | 1,835 | 1,760 |
| Woman, 30, 5 ft 5 in, 140 lb | 1,428 | 1,416 | 1,356 |
For overweight and obese adults, the Academy of Nutrition and Dietetics prefers Mifflin-St Jeor when resting metabolic rate cannot be measured directly (Academy of Nutrition and Dietetics).
Frequently asked questions
What is the best equation for BMR?
No equation is best for everyone. For overweight and obese adults, the Academy names Mifflin-St Jeor when resting metabolic rate cannot be measured (Academy of Nutrition and Dietetics).
Which Harris-Benedict equation does this calculator use?
This calculator uses the 1984 revision. For men, its constant is 88.362. For women, its constant is 447.593.
Is the Harris-Benedict equation BMR or RMR?
The equation predicts resting energy requirements (Roza and Shizgal, 1984). The label BMR is a convention used by calculators for the result.
Does the Harris-Benedict equation include exercise?
No. The equation estimates resting energy. An activity factor is applied separately to account for movement.
Is the Harris-Benedict equation different for women?
Yes. It is a separate equation with its own constant and coefficients. The women's equations appear alongside the men's equations in Table 1.
Can the Harris-Benedict equation be used for weight loss?
It estimates the energy a body uses. It does not set a target, and this page does not give one.
Sources
- Mifflin et al. Am J Clin Nutr 1990;51(2):241-7. PMID 2305711
- Roza AM, Shizgal HM. Am J Clin Nutr 1984;40(1):168-82. PMID 6741850
- Harris JA, Benedict FG. PNAS 1918;4(12):370-373. PMID 16576330
- Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, Publication 279, 1919, p. 190
- Pavlidou E, Papadopoulou SK, Seroglou K, Giaginis C. Metabolites 2023;13(2):189. PMID 36837808
- Academy of Nutrition and Dietetics EAL, Adult Weight Management: Determination of RMR
This calculator provides general information, not medical or nutritional advice. It does not diagnose or treat any condition. Talk to a qualified clinician or registered dietitian before making significant changes to what you eat.
Written by the Maintenance Calorie Calculator editorial team.