The Body's Engine: A Guide to Basal Metabolic Rate (BMR)

Your Basal Metabolic Rate, or BMR, represents the minimum number of calories your body needs to perform its most basic, life-sustaining functions at rest. Think of it as the energy your body would burn if you were to stay in bed, awake but completely still, for 24 hours. These essential functions include breathing, circulating blood, regulating body temperature, cell growth and repair, nerve function, and contracting muscles. Your BMR accounts for the largest portion of your total daily calorie expenditure, typically making up about 60-75% of the calories you burn each day. Understanding this number is the foundational step in managing weight, whether your goal is to lose, gain, or maintain your current weight.

This calculator uses the widely accepted Mifflin-St Jeor equation, which is considered one of the most accurate formulas for estimating BMR in a general population. By inputting your age, gender, height, and weight, the calculator provides your BMR value. But it doesn't stop there. Since we rarely spend our entire day at rest, the calculator then helps you determine your Total Daily Energy Expenditure (TDEE). By selecting your typical activity level—from sedentary to extra active—the calculator multiplies your BMR by an activity factor to give you a realistic estimate of the total number of calories you burn on an average day. This TDEE value is the crucial number you need for effective diet planning. To lose weight, you need to consume fewer calories than your TDEE. To gain weight, you need to consume more. To maintain your weight, you should aim to match your calorie intake to your TDEE. This tool empowers you to move beyond generic diet advice and start with a personalized, science-based target for your nutritional needs.

The BMR Formulas Explained

There are several formulas to estimate BMR. This calculator uses the Mifflin-St Jeor equation, which research has shown to be more accurate than the older Harris-Benedict equation.

Mifflin-St Jeor Equation for Men: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age (years) + 5
Mifflin-St Jeor Equation for Women: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age (years) - 161

Calculating Your Total Daily Energy Expenditure (TDEE)

Once your BMR is calculated, it is multiplied by an activity factor to estimate your TDEE:

Sedentary: (little or no exercise) - BMR × 1.2
Lightly active: (light exercise/sports 1-3 days/week) - BMR × 1.375
Moderately active: (moderate exercise/sports 3-5 days/week) - BMR × 1.55
Very active: (hard exercise/sports 6-7 days a week) - BMR × 1.725
Extra active: (very hard exercise/sports & physical job) - BMR × 1.9

BMR & Daily Calorie