Harris-Benedict Equation Calculators

0 calculators tagged with “Harris-Benedict Equation”

The Harris-Benedict equation is one of the most widely used formulas for estimating basal metabolic rate (BMR) — the number of calories your body burns at rest just to maintain basic physiological functions. Originally published in 1919 and revised in 1984, it uses height, weight, age, and sex to estimate energy needs. Multiplied by an activity factor, it gives total daily energy expenditure (TDEE) — a key starting point for designing diets, exercise programs, and clinical nutrition plans.

All Calculators

No calculators found for this topic.

What Is the Harris-Benedict Equation?

The Harris-Benedict equation estimates Basal Metabolic Rate (BMR) — the energy expended at complete rest in a thermoneutral environment after fasting. It accounts for four key variables: sex, weight, height, and age.

The Revised Harris-Benedict Formulas (1984)

Men:
BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years)

Women:
BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years)

Worked Example

A 35-year-old woman, 65 kg, 165 cm:
BMR = 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 35)
= 447.593 + 601.055 + 511.17 − 151.55
= 1,408 kcal/day

From BMR to TDEE: Activity Multipliers

Total Daily Energy Expenditure (TDEE) = BMR × Activity Factor:

  • Sedentary (little or no exercise): × 1.2
  • Lightly active (1–3 days/week exercise): × 1.375
  • Moderately active (3–5 days/week): × 1.55
  • Very active (6–7 days/week, hard exercise): × 1.725
  • Extra active (physical job + daily exercise): × 1.9

For the example above (moderately active): TDEE = 1,408 × 1.55 = 2,182 kcal/day

Mifflin-St Jeor Equation (Preferred for Most Adults)

The Mifflin-St Jeor equation (1990) is now considered more accurate than the original Harris-Benedict for most adults:

Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

Both equations overestimate BMR in obese individuals; for them, lean body mass–based equations (Katch-McArdle) are more accurate.

Glossary

Basal Metabolic Rate (BMR)
The energy expended by the body at complete rest in a thermoneutral environment after fasting — the minimum calories needed to sustain basic physiological functions. Accounts for approximately 60–70% of total daily energy expenditure.
Total Daily Energy Expenditure (TDEE)
The total calories burned per day by all activities combined — BMR plus the energy cost of physical activity, thermic effect of food, and non-exercise activity thermogenesis (NEAT). Estimated as BMR × activity factor.
Mifflin-St Jeor Equation
A 1990 update to BMR estimation formulas, generally more accurate than the original Harris-Benedict for normal-weight adults. Men: BMR = 10 × kg + 6.25 × cm − 5 × age + 5. Women: same but −161 instead of +5.

Frequently Asked Questions

The Harris-Benedict equation estimates Basal Metabolic Rate (BMR) — the calories burned at rest by basic physiological processes (breathing, circulation, cell maintenance). BMR accounts for roughly 60–70% of total daily energy expenditure. Multiplying BMR by an activity factor gives Total Daily Energy Expenditure (TDEE), the estimated total calories burned per day.

The Mifflin-St Jeor equation (1990) is generally considered more accurate for most adults, particularly those with healthy body weight. Multiple validation studies have found it predicts BMR within 10% of measured values in normal-weight individuals more reliably than the original Harris-Benedict. The American Dietetic Association recommends Mifflin-St Jeor as the preferred equation for estimating caloric needs.

TDEE = BMR × Activity Factor. Multiply your estimated BMR by the factor matching your typical weekly activity: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, or 1.9 for extremely active. The result estimates your average daily calorie expenditure, which you can use as a baseline for setting caloric intake targets.

BMR decreases with age primarily because of age-related loss of lean muscle mass (sarcopenia) — muscle tissue is metabolically active and burns significantly more calories at rest than fat tissue. Hormonal changes (declining testosterone, estrogen, and growth hormone) also contribute. The Harris-Benedict and Mifflin-St Jeor equations account for this by including age as a negative term in the formula.