What is the difference between Harris-Benedict and Mifflin-St Jeor?

Both estimate basal metabolic rate from sex, weight, height, and age. Mifflin-St Jeor (1990) is generally considered more accurate in modern populations, while the revised Harris-Benedict equation is the long-established reference. The tool shows both so you can compare.

How is total energy expenditure calculated?

Total daily energy expenditure equals BMR multiplied by an activity factor and a stress factor. The activity factor reflects mobility, while the stress factor accounts for the increased metabolic demand of illness, surgery, sepsis, or burns.

How much protein should a patient receive?

Protein needs are weight-based, typically 0.8 to 2.0 grams per kilogram per day depending on clinical state. Critically ill or catabolic patients often need 1.2 to 2.0 g/kg/day, which the tool estimates from the selected protein factor.

Should I use actual or adjusted body weight?

For patients within a healthy weight range, use actual body weight. For obese patients many units use an adjusted body weight to avoid overfeeding. Enter the weight your protocol specifies; the equations apply it directly.

Nutritional Requirements Calculator (Harris-Benedict / Mifflin)

Clinical energy and protein requirements

Estimating a patient’s energy and protein needs is the foundation of clinical nutrition support, whether enteral, parenteral, or oral. This calculator computes basal metabolic rate (BMR) with two established equations, scales it to total daily energy expenditure (TDEE) using activity and stress factors, and derives a weight-based protein target.

How it works

The Mifflin-St Jeor equation is:

Men:   BMR = 10*weight + 6.25*height - 5*age + 5
Women: BMR = 10*weight + 6.25*height - 5*age - 161
(weight in kg, height in cm, age in years)

The revised Harris-Benedict equation is:

Men:   BMR = 88.362 + 13.397*weight + 4.799*height - 5.677*age
Women: BMR = 447.593 + 9.247*weight + 3.098*height - 4.330*age

Total daily energy expenditure is then TDEE = BMR x activity factor x stress factor. The protein target is protein g/day = weight (kg) x protein factor (g/kg).

Tips and notes

Mifflin-St Jeor is usually preferred for current populations, but both are shown for comparison and to match local protocols. Stress factors meaningfully increase requirements in sepsis, major surgery, trauma, and burns. Reassess as the clinical state changes, and use adjusted body weight in obesity to avoid overfeeding. These are estimates; indirect calorimetry remains the gold standard where available.