Harris Benedict Calculator

The Harris-Benedict equation, and its long history

If you are here, you probably want the Harris-Benedict number specifically, maybe because a coach, a form, or an old habit asks for it. This calculator gives you that, and this page is honest about where the equation came from and where a newer one might serve you better.

Harris-Benedict is the granddaddy of calorie formulas. It began with a study by James Harris and Francis Benedict, published in 1919 by the Carnegie Institution, that measured the resting energy of a few hundred people and turned the pattern into an equation for basal metabolic rate, the calories your body burns just to stay alive at rest. For most of a century it was the standard everything else was measured against.

It has been updated since. Roza and Shizgal reworked the numbers in 1984 to fit populations better, and that 1984 version is the one this tool uses, and the one most calculators mean when they say "Harris-Benedict". After the resting figure, the tool applies your activity level to estimate the calories you burn across a full day.

The formula this calculator uses

This calculator runs the revised 1984 Harris-Benedict equations, not the 1919 originals. In their sex-separated form:

Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years)

Weight in kilograms, height in centimetres, age in years, with pounds and inches converted for you. The coefficients look fussier than they need to be, but they are simply the best-fit numbers Roza and Shizgal landed on when they re-ran the original data with newer methods.

A worked example

Take a 35 year old woman, 168 cm tall, 70 kg. Into the women's line:

BMR = 447.593 + (9.247 × 70) + (3.098 × 168) − (4.330 × 35)
BMR = 447.593 + 647.29 + 520.464 − 151.55
BMR ≈ 1464 Calories/day

So her resting burn lands near 1,464 calories. If she does moderate exercise a few times a week, a factor of 1.55, the tool multiplies through to about 1464 × 1.55, or roughly 2,270 calories a day as her estimated total.

Turning BMR into daily calories

Your resting rate is not your daily need, since real days involve moving around. The calculator applies an activity factor to the BMR and reports the result as your Total Daily Energy Expenditure (TDEE), with a table of every level. The factors are:

The activity step swings the answer hard, often several hundred calories between neighbouring levels, and it is the roughest part of the whole calculation. People tend to place themselves a level or two above where they honestly sit. Choose conservatively, and use the result as a starting figure to refine against real life rather than a number to obey.

Harris-Benedict or Mifflin-St Jeor?

This is the honest bit. Harris-Benedict works, but it is no longer the most accurate option for most people. When researchers put the common equations against actual lab measurements, the newer Mifflin-St Jeor equation came within about 10 percent of the true value more often. Harris-Benedict, even in its 1984 form, tends to read a touch high.

So why keep a Harris-Benedict tool at all? Because it is still widely taught, still written into plenty of forms and programmes, and the difference between it and Mifflin-St Jeor is usually only a hundred calories or so, comfortably inside the margin of any resting estimate. If you specifically need Harris-Benedict, this is it. If you just want the best general estimate, the Mifflin-St Jeor Calculator is the one to reach for, and our plain BMR Calculator runs that same newer equation.

Where the estimate can be off

Beyond the equation-choice question, the usual honest limits apply to any formula like this:

• It cannot see body composition. Same age, height, weight and sex gives the same number, whether you are mostly muscle or not, even though muscle burns more at rest.
• It reads high for modern, less active bodies. This is the specific weakness Harris-Benedict is known for, and the reason both the 1984 revision and the later Mifflin-St Jeor equation exist.
• Health shifts it. Thyroid problems, medications, pregnancy, breastfeeding and illness all move real energy needs beyond what height and weight predict.
• The daily total is an estimate. The activity multiplier is a broad bracket, so the TDEE is a starting point, not a target carved in stone.

For general planning it is perfectly serviceable. For anything medical, or if a health condition affects your metabolism, use it as background and confirm with a doctor or dietitian.

Questions people ask

Does this use the original or the revised Harris-Benedict?

The revised one, from Roza and Shizgal in 1984. That is the version most tools mean by "Harris-Benedict", and it corrects some of the overestimation in the 1919 original. You can see the exact coefficients in the formula section above.

Why is my Harris-Benedict number higher than Mifflin-St Jeor?

Because it usually is. Harris-Benedict tends to read a little high for modern bodies, which is exactly why Mifflin-St Jeor was developed. The gap is normally around a hundred calories, comfortably within the margin of either estimate.

Which should I actually use?

If something specifically asks for Harris-Benedict, use this. If you are free to choose and want the best general accuracy, Mifflin-St Jeor is the better pick for most people. Either way, treat the result as an estimate to refine, not a hard fact.

References

Where the figures come from. This tool runs the 1984 Harris-Benedict revision by Roza and Shizgal, and those coefficients are quoted above from their paper. The original equation traces to Harris and Benedict's 1919 Carnegie monograph. And the finding that the newer Mifflin-St Jeor equation is generally more accurate comes from a systematic review by the Academy of Nutrition and Dietetics.

1. Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition. 1984;40(1):168-182. https://doi.org/10.1093/ajcn/40.1.168
2. Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Washington, DC: Carnegie Institution of Washington; 1919. Publication No. 279.
3. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775-789. https://doi.org/10.1016/j.jada.2005.02.005