What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate (BMR) represents the minimum number of calories your body requires to perform its most basic, life-sustaining functions while at rest. Think of it as the energy you would expend if you were to stay in bed all day, not moving. These essential functions include breathing, circulating blood, regulating body temperature, cell production, and nutrient processing. Understanding this baseline is the crucial first step in creating a personalized nutrition and fitness plan, and this BMR calculator provides that foundational number.
BMR vs. TDEE: From Resting to Real Life
While BMR is your body's "idle" speed, it doesn't account for your daily movements—from walking to the kitchen to running a marathon. To get a realistic picture of your daily calorie needs, you need to calculate your Total Daily Energy Expenditure (TDEE). TDEE is determined by multiplying your BMR by an activity factor that corresponds to your lifestyle.
This calculator uses the widely accepted Mifflin-St Jeor equation to find your BMR and then applies your selected activity level to estimate your TDEE, which is presented as your "Daily Calorie Needs" for weight maintenance. This TDEE figure is your caloric break-even point. To lose weight, you need to consume fewer calories than your TDEE, creating a calorie deficit. For example, a consistent deficit of 500 calories per day generally leads to about 1 pound (0.5 kg) of weight loss per week. To get a quick check of where your weight currently stands, you can use our BMI Calculator.
How BMR is Calculated: The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor equation, which research has shown to be more accurate than the older Harris-Benedict formula. The calculations are as follows:
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age - 161
As the formulas show, factors like weight, height, age, and sex significantly impact your BMR. Men typically have a higher BMR due to generally higher muscle mass, and BMR tends to naturally decrease with age. For a deeper dive into the science of metabolism, resources from reputable health organizations like the Harvard Health Publishing offer valuable insights.