Harris-Benedict BMR Calculator

The Harris-Benedict equation is the classic BMR formula, revised by Roza and Shizgal in 1984. Enter your stats; the Mifflin-St Jeor figure is shown alongside for comparison.

The revised Harris-Benedict equation

For weight in kilograms, height in centimetres and age in years:

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

Worked example

A 30-year-old man, 180 cm, 80 kg: 88.362 + (13.397 × 80) + (4.799 × 180) − (5.677 × 30) = 88.362 + 1071.76 + 863.82 − 170.31 = 1,854 calories/day. Mifflin-St Jeor for the same person gives 1,780 — Harris-Benedict reads about 74 calories (4%) higher, which is the typical gap.

When to use Harris-Benedict instead of Mifflin-St Jeor

Rarely, on accuracy grounds — Mifflin-St Jeor is the better general-population equation. Reach for Harris-Benedict when you need to match a figure from an older calculator, a textbook, or a study that used it, so you are comparing like with like. If you do use it for planning, know it runs about 5% high and set your deficit from TDEE, not from BMR.

From BMR to a calorie target

BMR is not a target — nobody lies still all day. Multiply it by an activity factor with the TDEE calculatorto get maintenance calories, adjust up or down for a goal with the calorie calculator, then split the target with the macro calculator. For the body-fat input this page can use, see the body fat calculator.

The other BMR equations

Mifflin-St Jeor — the modern default, and the parent calculator.
Katch-McArdle — Uses lean body mass instead of total weight — more accurate if you know your body fat and are lean or muscular.

Source: Harris & Benedict 1919, revised by Roza & Shizgal 1984.

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Frequently asked questions

Harris-Benedict or Mifflin-St Jeor — which should I trust?

For most people, Mifflin-St Jeor. When the two were tested against measured resting energy expenditure, Mifflin-St Jeor was accurate within 10% more often, and Harris-Benedict tended to over-predict by roughly 5%. Harris-Benedict is still worth calculating because so many older tools, textbooks and studies use it — knowing both lets you compare figures on a like-for-like basis.

What did the 1984 revision change?

Roza and Shizgal re-derived the constants from the original Harris-Benedict data plus additional subjects, correcting a small systematic bias. The 1984 version (the one used here) reads a little lower than the 1919 original. If a source quotes the '66.5 / 655' constants it is using the 1919 equation; this page uses the revised '88.362 / 447.593' constants.

Why does it read higher than Mifflin?

It was fitted to a smaller, early-20th-century sample that was, on average, more physically active with a different body composition than today's population. The result is a formula that assumes a slightly higher resting burn for the same age, height and weight.

Is BMR the same as the calories I should eat?

No. BMR is what you would burn lying still all day. Multiply it by an activity factor to get maintenance calories (TDEE), then adjust for a goal. Eating at your BMR is usually too low.

How accurate is any BMR equation for me?

Expect ±10% for most people, more if you are very tall, very short, very lean or carrying a lot of muscle. A metabolic cart test (indirect calorimetry) is the accurate measurement; the equations are a free approximation. Track your weight for two to three weeks and adjust the number to what your body actually does.

Does Harris-Benedict work for older adults?

It is less reliable past about 65, where it tends to over-predict further because age-related muscle loss outpaces what the linear age term assumes. For older or very sedentary people, Mifflin-St Jeor or the lean-mass-based Katch-McArdle is a better choice.

Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.