Harris Health System Calculator

The Harris-Benedict equation is a method used to estimate an individual's Basal Metabolic Rate (BMR), which is the number of calories your body needs to maintain basic physiological functions at rest. This calculator implements the revised Harris-Benedict equation, which provides more accurate results than the original 1919 version.

What is the Harris-Benedict Equation?

The Harris-Benedict equation is a widely used formula to estimate the number of calories a person needs to maintain their weight. It was developed by Dr. Frank Benedict and later revised by Dr. Charles Harris in 1984. The equation takes into account age, weight, height, and gender to calculate BMR.

Note: The Harris-Benedict equation provides an estimate. Individual calorie needs may vary based on factors like activity level, genetics, and overall health.

Key Concepts

Basal Metabolic Rate (BMR): The number of calories needed while at complete rest.
Total Daily Energy Expenditure (TDEE): The total number of calories burned per day, including activity.
Revised Equation: The 1984 revision provides more accurate results than the original 1919 version.

How to Use This Calculator

Select your gender (male or female)
Enter your age in years
Enter your weight in pounds
Enter your height in inches
Click "Calculate" to see your BMR

Tip: For more accurate results, use the calculator after a 12-hour fast and before eating or drinking anything.

Formula Used

The calculator uses the following formulas for men and women:

For Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years) For Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)

The calculator automatically converts pounds to kilograms and inches to centimeters before performing the calculation.

Worked Example

Let's calculate the BMR for a 30-year-old woman who weighs 150 pounds and is 5'6" tall (66 inches).

Convert weight to kg: 150 lbs × 0.453592 = 68.0388 kg
Convert height to cm: 66 inches × 2.54 = 167.64 cm
Plug values into the formula:
BMR = 447.593 + (9.247 × 68.0388) + (3.098 × 167.64) - (4.330 × 30) BMR = 447.593 + 629.36 + 516.59 - 129.9 BMR = 1,463.65 calories/day

This woman would need approximately 1,464 calories per day to maintain her weight at complete rest.

Interpreting Results

Your BMR result represents the number of calories needed to maintain basic physiological functions at rest. To calculate your Total Daily Energy Expenditure (TDEE), multiply your BMR by an activity factor:

Activity Level	Multiplier
Sedentary (little or no exercise)	1.2
Lightly active (light exercise 1-3 days/week)	1.375
Moderately active (moderate exercise 3-5 days/week)	1.55
Very active (hard exercise 6-7 days/week)	1.725
Athlete (intense exercise daily)	1.9

For example, a moderately active woman with a BMR of 1,464 calories would need approximately 2,270 calories per day (1,464 × 1.55).

FAQ

Is the Harris-Benedict equation accurate?: The Harris-Benedict equation provides a good estimate but may not be perfectly accurate for everyone. Individual variations in metabolism can affect calorie needs.
Can I use this calculator for children?: The Harris-Benedict equation is designed for adults. For children, specialized formulas like the Schofield equation are more appropriate.
How often should I recalculate my BMR?: Your BMR changes with age, weight, and height. It's a good idea to recalculate every few months, especially if you're experiencing significant weight changes.
What if I'm pregnant or breastfeeding?: Pregnant and breastfeeding women have increased calorie needs. Specialized formulas account for these additional requirements.
Can I use this calculator for weight loss?: Yes, understanding your BMR helps set realistic calorie goals for weight management. Combine your BMR with activity level and subtract 200-500 calories for weight loss.