CALCULATOR

Harris-Benedict Calculator

The revised 1984 equation, with the original for reference and a direct comparison against Mifflin-St Jeor at four body types.

Result

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BMR–

Daily burn at your activity–

Mifflin-St Jeor–

Harris-Benedict–

Katch-McArdle–

Spread between them–

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The Harris-Benedict equation

The original Harris-Benedict equation dates from 1919, making it the oldest of the widely used BMR formulas. The version in general use today is the Roza and Shizgal revision from 1984, which corrected the original against better data. This calculator uses the revised version.

It tends to read slightly higher than Mifflin-St Jeor, commonly by 50 to 100 kcal, because it was derived from a population that differed from the modern average in body composition and activity.

It remains widely used and is perfectly serviceable. If you have been using it consistently and adjusting from real results, there is no reason to switch. Where it matters is comparing figures between calculators without knowing which equation each one uses.

The equations, original and revised

Revised Harris-Benedict (Roza and Shizgal, 1984)Men: BMR = (13.397 x W) + (4.799 x H) - (5.677 x A) + 88.362
Women: BMR = (9.247 x W) + (3.098 x H) - (4.330 x A) + 447.593

Original Harris-Benedict (1919), for reference onlyMen: BMR = (13.75 x W) + (5.003 x H) - (6.755 x A) + 66.5
Women: BMR = (9.563 x W) + (1.850 x H) - (4.676 x A) + 655.1

How it compares with Mifflin-St Jeor

Person	Harris-Benedict	Mifflin-St Jeor	Difference
Man, 80 kg, 175 cm, 30	1,822 kcal	1,749 kcal	+73
Woman, 65 kg, 165 cm, 30	1,406 kcal	1,370 kcal	+36
Man, 95 kg, 180 cm, 50	1,928 kcal	1,830 kcal	+98
Woman, 55 kg, 160 cm, 25	1,325 kcal	1,264 kcal	+61

Harris-Benedict reads consistently higher. The gap widens with body size and age. Both figures sit inside each other error bands, which is the practical point: neither is precise enough for the difference to matter as much as consistent tracking does.

Frequently asked questions

Is Harris-Benedict outdated?

The 1919 original is. The 1984 revised version is still in common use, though Mifflin-St Jeor generally performs better in comparison studies.

Why is Harris-Benedict higher than Mifflin?

Different derivation populations. The gap is typically 50 to 100 kcal, which is within the error band of both.

Which should I use?

Either, used consistently. Adjusting from two to three weeks of real weight data matters more than the equation you start with.

What is the revised Harris-Benedict formula?

Men: 13.397W + 4.799H - 5.677A + 88.362. Women: 9.247W + 3.098H - 4.330A + 447.593.

Sources

Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. PNAS, 1918.
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition, 1984.
National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
NHS. Nutrition and health guidance. nhs.uk
US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov

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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.