Harris-Benedict Calculator (BMR and Daily Calories)
Calculate your basal metabolic rate with the Harris-Benedict equation (original 1919 or revised 1984) and your daily calorie needs for five activity levels.
How it works
Revised (1984) — men: 88.362 + 13.397W + 4.799H − 5.677A · women: 447.593 + 9.247W + 3.098H − 4.330A · Original (1919) — men: 66.473 + 13.7516W + 5.0033H − 6.755A · women: 655.0955 + 9.5634W + 1.8496H − 4.6756A (W kg, H cm, A years; kcal/day) · daily needs = BMR × activity factor
James Harris and Francis Benedict published their basal metabolism equations in 1918–1919 from calorimetry on 239 adults, and they remained the clinical standard for most of the 20th century. Roza and Shizgal re-fitted the coefficients to the original data plus newer measurements in 1984. Both versions give similar results for most adults and tend to run about 5% higher than the Mifflin-St Jeor equation; multiplying BMR by an activity factor estimates total daily calories.
Worked example
A 30-year-old man, 70 kg and 175 cm, revised equation: BMR = 88.362 + 13.397 × 70 + 4.799 × 175 − 5.677 × 30 = 88.362 + 937.79 + 839.83 − 170.31 = 1,696 kcal/day. Moderately active (× 1.55): about 2,628 kcal/day. The original 1919 equation gives 1,702 kcal/day.
Sources: Harris JA, Benedict FG (1918) A biometric study of human basal metabolism. PNAS 4:370–373 · Roza AM, Shizgal HM (1984) The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 40:168–182
Frequently asked questions
What is the Harris-Benedict equation?
It is a formula that estimates basal metabolic rate — the calories your body uses at complete rest — from sex, weight, height and age. Multiply the result by an activity factor between 1.2 and 1.9 to estimate how many calories you need per day.
Should I use the original or the revised equation?
The revised 1984 version by Roza and Shizgal is the one most calculators use today; the original is still taught in many nutrition courses. They usually differ by less than 1–2%, so either is fine for planning.
Is Harris-Benedict more accurate than Mifflin-St Jeor?
Studies comparing equations with measured metabolic rate found Mifflin-St Jeor slightly more accurate in modern adults, especially those with overweight; Harris-Benedict tends to overestimate by a few percent. Both have errors of about ±10% for individuals.
How do I use the result to lose weight?
Start from your daily calorie needs (BMR × activity factor) and eat about 300–500 kcal less per day for gradual loss. Re-check after a few weeks, because the estimate is only a starting point.
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This calculator gives general nutrition estimates and is not medical advice. Energy and nutrient needs vary between people; children, pregnant people and anyone with a medical condition should follow a doctor or registered dietitian.