Harris-Benedict BMR Calculator
Basal metabolic rate is the number of calories your body uses at complete rest to keep its core functions running. The Harris-Benedict equation estimates BMR from your weight, height, age, and sex, and is one of the most widely cited predictive equations in nutrition. This calculator uses the 1984 Roza and Shizgal revision of the original 1919 study, then multiplies BMR by an activity factor to estimate your total daily energy expenditure, the calories needed to maintain your current weight. Enter your details in metric units and choose an activity level to see both figures. Treat the result as a starting estimate and refine it against your actual weight trend.
Harris-Benedict formula (1984 revision)
Men: BMR = 88.362 + 13.397*weight(kg) + 4.799*height(cm) - 5.677*age
Women: BMR = 447.593 + 9.247*weight(kg) + 3.098*height(cm) - 4.330*age
TDEE = BMR * activity factor
Mild loss = TDEE - 250; mild gain = TDEE + 250
Worked example: a 30-year-old man, 70 kg and 175 cm gives BMR = 88.362 + 937.79 + 839.825 - 170.31 = 1,695.67 kcal/day. At a moderate factor of 1.55 the TDEE is 2,628.28 kcal/day.
How to use the result
- BMR is resting energy only; daily needs are higher once activity is added through the factor.
- The mild loss and gain rows apply a 250 kcal/day adjustment, roughly half a pound per week of body-weight change.
- Predictive equations estimate group averages; verify against your own weight trend over several weeks.
- Recalculate as your weight changes, because BMR scales with body mass.
- This tool is for general education and is not medical or dietetic advice.
Harris-Benedict BMR: frequently asked questions
What is the Harris-Benedict equation?
The Harris-Benedict equation estimates basal metabolic rate (BMR), the calories your body burns at rest, from weight, height, age, and sex. This tool uses the 1984 Roza and Shizgal revision: for men, BMR = 88.362 + (13.397 times weight in kg) + (4.799 times height in cm) minus (5.677 times age). For women, BMR = 447.593 + (9.247 times weight in kg) + (3.098 times height in cm) minus (4.330 times age).
How do I turn BMR into total daily calories?
Multiply BMR by an activity factor. Common factors are 1.2 for sedentary, 1.375 for light activity, 1.55 for moderate activity, 1.725 for very active, and 1.9 for extra active. The result is your total daily energy expenditure (TDEE), an estimate of the calories needed to maintain your current weight.
Is the Harris-Benedict equation accurate?
It is an estimate. Predictive equations like Harris-Benedict approximate group averages and can differ from an individual's measured metabolic rate, especially at the extremes of body composition. They are useful starting points but should be adjusted based on real-world weight change over time.
What units does this calculator use?
Enter weight in kilograms, height in centimetres, and age in years. To convert, 1 pound is about 0.4536 kg and 1 inch is 2.54 cm. The result is returned in kilocalories per day, the unit commonly labelled as Calories on US food packaging.
Why does sex change the result?
The equation uses different constants and coefficients for men and women because, on average, body composition differs: men typically carry more lean mass, which is more metabolically active at rest. Select the option that matches the sex assigned for the equation you intend to use.
Official sources
- National Center for Biotechnology Information (PubMed): Roza and Shizgal 1984 revised Harris-Benedict equation literature.
- U.S. Centers for Disease Control and Prevention: Healthy weight and energy balance guidance.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.