BEE Calculator — Basal Energy Expenditure (Harris-Benedict)

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How this is calculated

Basal Energy Expenditure (BEE) is the minimum number of kilocalories the body needs at complete rest to maintain vital functions — breathing, circulation, cell repair and thermoregulation. This calculator uses the revised Harris-Benedict equation published by Roza and Shizgal in 1984, which refined the original 1919 coefficients using indirect calorimetry on a wider population. Men have higher BEE due to greater lean body mass; the sex-specific constants encode this difference. BEE is expressed in kcal per day and provides the foundation for clinical nutrition prescriptions.

In clinical settings, BEE is multiplied by two correction factors. The stress factor accounts for the increased metabolic demand of illness or injury: minor illness ≈ 1.1–1.2, moderate surgery or trauma ≈ 1.3–1.4, severe sepsis or major burns can reach 1.5–2.0. The activity factor adjusts for physical activity: bed-rested patients use 1.0, ambulatory patients about 1.2, and healthy individuals up to 1.55 for moderate activity. Total Energy Expenditure (TEE) = BEE × stress factor × activity factor.

The Harris-Benedict equation is still widely used in clinical dietetics because it is well-validated across many populations. It uses only four variables (weight, height, age, sex) and therefore cannot account for body composition — very muscular or very obese individuals may see systematic over- or under-estimates. The Mifflin-St Jeor equation is sometimes preferred for healthy weight-management calculations; Harris-Benedict is more prevalent in clinical nutrition protocols.