Harris–Benedict Calculator & Formula
Estimates your basal metabolic rate (BMR) — the energy you burn at rest — from weight, height, age and sex. There are two versions, and which one a site uses actually matters.
The Harris–Benedict equation comes in two forms: the 1919 original and the 1984 Roza–Shizgal revision, which re-derived it on newer measurements. Most calculators just say "Harris–Benedict" without saying which — so WIMSTA runs both, labels the year, and shows them alongside Mifflin–St Jeor and other equations as a range.
On these inputs the two Harris–Benedict versions differ by 11 kcal/day (0.8%) — the revision usually sits a little lower. Small, but it's why a page should say which Harris–Benedict it uses. At moderate activity that's roughly 2190 vs 2173 kcal of maintenance energy. The full calculator also runs Mifflin–St Jeor, WHO/FAO and Katch–McArdle — a range, not one number.
Two formulas, one name
In 1984, Roza and Shizgal re-evaluated Harris–Benedict against modern indirect-calorimetry data on a new sample of n = 337, indirect calorimetry, and published updated coefficients (Am J Clin Nutr 40(1):168–182). Because it's a re-derivation on independent data — not a reissue — it counts as its own estimate, so both versions legitimately appear in our range rather than one being "the" formula.
For everyday adults the two land within about 1% of each other, with the revision usually a touch lower — small, but real, and a reason to always say which Harris–Benedict.
Good for
A quick resting-energy baseline from four everyday numbers, and tracking your own trend over time.
Runs high
Both versions tend to overestimate modern BMR by ~5% vs the newer Mifflin–St Jeor equation. Not valid in pregnancy or for under-18s.
One equation is a guess. See the range.
Harris–Benedict (both years), Mifflin–St Jeor, WHO/FAO and Katch–McArdle rarely agree to the calorie. The calculator shows the honest range and turns it into maintenance calories.
Open the calorie calculatorOriginal: Harris & Benedict (1919), Carnegie Inst. of Washington, Pub. 279. Revision: Roza & Shizgal (1984), Am J Clin Nutr 40(1):168–182, measured resting energy expenditure. Both coefficient sets are the ones implemented in our engine and covered by the test suite.
FAQ
Which Harris–Benedict formula is correct — 1919 or 1984?
Both are "Harris–Benedict". The 1919 original is the historical equation; the 1984 Roza–Shizgal version re-derived it on new measurements and is a little more accurate. WIMSTA shows both and treats them as two estimates, not one right answer — which is why we always label the year.
What is the difference between the two versions?
The coefficients differ because the 1984 revision was fitted on a new sample (n=337), not a reissue of the old one. For ordinary adults the two land within about 1% of each other — usually the revision is slightly lower. The gap widens a little at the extremes of age or body size.
Is the Harris–Benedict equation accurate?
It is a solid population estimate but tends to overestimate resting metabolism by roughly 5% for modern populations compared with the newer Mifflin–St Jeor equation. Good for tracking your own trend; not a precise personal number. Read it as part of a range.
How do I turn BMR into daily calories?
Multiply BMR by an activity factor — about 1.2 if sedentary up to ~1.9 if very active — to get maintenance calories (TDEE). The calculator does this and shows the range across every BMR equation.
How every formula is sourced: the method page.