BMR Calculator

What is a BMR Calculator?

A Basal Metabolic Rate (BMR) Calculator estimates the number of calories your body needs to perform its most basic, life-sustaining functions while at rest. These functions include breathing, circulation, nutrient processing, and cell production. BMR is the largest component of your Total Daily Energy Expenditure (TDEE).

Understanding your BMR can be a foundational step in managing your weight, as it helps you determine a baseline for your daily caloric needs. Whether your goal is weight loss, maintenance, or gain, knowing your BMR allows for more informed decisions about diet and physical activity. It represents the minimum amount of energy your body requires if you were to do nothing but rest for 24 hours.

BMR Calculation Formulas

This calculator primarily uses the Mifflin-St Jeor equation, which is widely considered one of the most accurate formulas for estimating BMR in modern populations. Optionally, the Harris-Benedict equation (revised) is also available.

Mifflin-St Jeor Equation (1990)

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

Where:

• Weight is in kilograms (kg)
• Height is in centimeters (cm)
• Age is in years

Revised Harris-Benedict Equation (1984)

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

The calculator handles unit conversions if you input height in feet/inches or weight in pounds.

How to Calculate BMR: Example (Mifflin-St Jeor)

Let's calculate the BMR for a 35-year-old woman who is 165 cm (approx. 5'5") tall and weighs 60 kg (approx. 132 lbs):

1. Identify Inputs:
   • Sex: Female
   • Weight: 60 kg
   • Height: 165 cm
   • Age: 35 years
2. Apply the Mifflin-St Jeor formula for women: BMR = (10 × 60) + (6.25 × 165) - (5 × 35) - 161
3. Calculate each part:
   • (10 × 60) = 600
   • (6.25 × 165) = 1031.25
   • (5 × 35) = 175
4. Complete the calculation: BMR = 600 + 1031.25 - 175 - 161 = 1295.25 kcal/day.

This calculator will provide this estimated BMR value. TDEE (Total Daily Energy Expenditure) calculators often use BMR as a starting point and then multiply it by an activity factor.

Common Applications of BMR Calculation

• Weight Management: Forms the basis for creating a calorie surplus (for gain) or deficit (for loss).
• Diet Planning: Helps in setting daily calorie targets for meal plans.
• Fitness Regimens: Athletes and fitness enthusiasts use BMR to fine-tune energy intake for performance and recovery.
• Clinical Settings: Used by dietitians and doctors to assess nutritional needs, especially for patients with specific metabolic conditions.
• Understanding Metabolism: Provides insight into one's baseline metabolic rate, which can vary based on factors like age, sex, body size, and composition.