BMR Calculator — Harris-Benedict Equation
Calculate your Basal Metabolic Rate using the Harris-Benedict equation — either the original 1918 version or the more accurate 1984 Roza–Shizgal revision — and multiply by an activity factor to find your daily calorie needs.
Equation version
Sex
kg
cm
years
Activity level
Calories burned at complete rest — Harris-Benedict equation
- 1
Weight component
13.397 × 70 = 937.8 - 2
Height component
4.799 × 175 = 839.8 - 3
Age component
5.677 × 30 = 170.3 - 4
BMR (Harris-Benedict)
88.362 + 937.8 + 839.8 − 170.3 = 1,696Intercept 88.362 from the Roza-Shizgal 1984 male equation.
How does this calculator work?
The Harris-Benedict equation estimates BMR from weight (kg), height (cm), age, and sex. The 1984 Roza–Shizgal revision is recommended: for men, BMR = 88.362 + 13.397·kg + 4.799·cm − 5.677·age; for women, BMR = 447.593 + 9.247·kg + 3.098·cm − 4.330·age. Multiply BMR by an activity factor (1.2–1.9) to get TDEE — your daily calorie maintenance level.
Formula
How this is calculated
The Harris-Benedict equation was the first widely-adopted formula for estimating Basal Metabolic Rate (BMR) — the calories the body burns at complete rest to sustain vital functions. The original version was published in 1918–1919 by James Arthur Harris and Francis Gano Benedict after measuring energy expenditure in a large sample of adults. It requires four inputs: weight in kilograms, height in centimetres, age in years, and biological sex, which determines which set of coefficients to use because men and women differ in average lean mass.
In 1984, Roza and Shizgal re-derived the coefficients using a larger, more representative dataset and corrected some statistical issues in the original work. The revised equation is generally preferred today; the calculator offers both so you can compare. Neither version accounts for body composition: a very muscular person will have their BMR underestimated, and someone with low lean mass may have it overestimated.
Total Daily Energy Expenditure (TDEE) is found by multiplying BMR by a physical activity level (PAL) factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, and 1.9 for extremely active. TDEE represents the calories needed to maintain current weight. Eating below TDEE causes weight loss; eating above it causes weight gain. The Mifflin-St Jeor equation (1990) is another widely used alternative that some studies find slightly more accurate for the modern population.
Frequently asked questions
The original (1918–1919) and revised (1984, Roza & Shizgal) versions use the same variables — weight, height, age, and sex — but with different coefficients. Roza and Shizgal re-estimated the constants from a larger sample and corrected a bias in the original work. The revised equation is considered more accurate for the general modern population.
Both equations use the same four inputs. Several validation studies, including one by Frankenfield et al. (2005), found the Mifflin-St Jeor equation (1990) to be slightly more accurate for estimating BMR in non-obese adults. Harris-Benedict (revised) remains widely used and gives similar results for most people; the difference is rarely more than 50–100 kcal/day.
Sedentary (desk job, little exercise) → 1.2. Light (1–3 days/week of exercise) → 1.375. Moderate (3–5 days/week) → 1.55. Active (6–7 days/week of vigorous exercise) → 1.725. Very active (daily heavy exercise or a physically demanding job) → 1.9. Most people overestimate their activity level, so starting with the factor one step lower than you think and adjusting based on real weight change is a reliable strategy.
Also known as
TG we-Calculate Editorial Team. (2026). BMR Calculator — Harris-Benedict Equation [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bmr-harris-benedict-equation-calculator
TG we-Calculate Editorial Team. "BMR Calculator — Harris-Benedict Equation." TG we-Calculate. 2026. https://we-calculate.com/calculator/bmr-harris-benedict-equation-calculator.
TG we-Calculate Editorial Team, "BMR Calculator — Harris-Benedict Equation," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bmr-harris-benedict-equation-calculator
@misc{wecalculate_bmr_harris_benedict_equation_calculator, title = {BMR Calculator — Harris-Benedict Equation}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bmr-harris-benedict-equation-calculator}}, year = {2026}, note = {TG we-Calculate} }
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