Harris-Benedict Calculator

The Harris-Benedict equation is the oldest of the BMR formulas still in everyday use. It was first published in 1919 and then revised in 1984 by Roza and Shizgal, who re-fitted its coefficients against better data; that revised version is the one this calculator runs. Like every BMR equation it takes weight, height and age and applies a separate constant and set of multipliers for men and women, returning the calories a body burns at complete rest. For decades it was the default figure in dietetics textbooks and clinical practice, which is why so many established programmes, apps and coaching templates are still built around its output. Knowing that lineage helps explain why two calculators can hand you slightly different numbers for the same body — they may simply be running different equations, each internally consistent.

The Harris-Benedict BMR describes a resting body, so on its own it understates what you actually burn. To reach a usable daily figure the calculator multiplies it by an activity factor — 1.2 for a sedentary week through to 1.9 for very heavy training — and the product is your Total Daily Energy Expenditure, the maintenance level where weight stays put. Because the multiplier does the heavy lifting, an honest read of your week matters more than the choice of formula: most people overstate how active they are and pick a tier too high. For the full activity table and every formula option in one place, this page’s parent is the TDEE Calculator, and once you have a daily number the Macro Calculator splits it into protein, carbohydrate and fat.

For a modern, mostly desk-bound population the revised Harris-Benedict equation tends to read a little high — often a few per cent above what a metabolic cart would measure — which is the main reason the 1990 Mifflin-St Jeor equation has overtaken it as the general default. That does not make Harris-Benedict wrong; it makes it a known quantity. The practical reason to choose it is alignment: if your coach, your tracking app or a plan you are following calculates with Harris-Benedict, matching the formula keeps every number on the same footing instead of introducing a gap you then have to reconcile. To see the two equations side by side for your own body, use the Mifflin-St Jeor Calculator. These figures are general estimates for healthy adults, not medical advice.