Harris-Benedict Calculator

This calculator uses the revised Harris-Benedict equation (Roza & Shizgal, 1984) to estimate basal metabolic rate (BMR) -- the calories the body burns at complete rest just to maintain basic function -- from weight, height, age, and sex, using separate published coefficients for men and women. From that baseline, it reports two different scaled-up estimates depending on the setting: Total Daily Energy Expenditure (TDEE), which multiplies BMR by an activity factor (from 1.2 for a sedentary lifestyle up to 1.9 for very high activity) and is the relevant figure for a healthy, ambulatory individual's everyday caloric needs -- reported across all five common activity tiers side by side, rather than requiring you to pick one upfront -- and Clinical energy needs, which instead multiplies BMR by a clinical stress factor (1.0 for no added stress up to roughly 1.75 for major burns) and is the relevant figure for a hospitalized patient whose metabolic demands are elevated by illness or injury rather than physical activity -- the two multipliers are not meant to be combined, since a bedridden, critically stressed patient is not also being scaled for a high activity level.

A rough protein range is also suggested, widening from a lower target near maintenance-level stress up to a higher target as the stress factor increases, reflecting that protein needs typically rise with the degree of physiologic stress. The original 1919 Harris-Benedict equation is known to run somewhat high compared to directly measured energy expenditure; this 1984 revision, published by Anne Roza and Harry Shizgal in the American Journal of Clinical Nutrition, corrected that using updated reference data and is generally considered more accurate, though still an estimate -- indirect calorimetry, where available, remains more accurate than any predictive equation for an individual patient, and any clinical caloric prescription should be adjusted based on the patient's actual response, not fixed to a formula's output.