Basal Metabolic Rate (BMR) Calculator
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic, life-sustaining functions at rest. These functions include breathing, circulation, cell production, and nutrient processing. Understanding your BMR can be a crucial first step in managing your weight and optimizing your energy intake for your specific needs, whether for weight loss, weight gain, or maintenance.
The most common formulas used to estimate BMR are the Harris-Benedict Equation and the Mifflin-St Jeor Equation. The Mifflin-St Jeor Equation is generally considered more accurate for most people. We will use the Mifflin-St Jeor equation here.
Understanding Your BMR
Your Basal Metabolic Rate (BMR) represents the minimum energy your body requires to keep vital functions running while you are in a completely rested state. Think of it as the calories your body burns just to stay alive – to keep your heart beating, your lungs breathing, your brain functioning, and to maintain your body temperature.
Factors Influencing BMR:
- Age: BMR generally decreases with age as muscle mass tends to decline.
- Gender: Men typically have a higher BMR than women due to having more muscle mass on average.
- Body Composition: Muscle tissue burns more calories at rest than fat tissue. Therefore, individuals with more muscle mass will have a higher BMR.
- Body Size: Larger individuals generally have a higher BMR.
- Genetics: Your genes play a role in determining your metabolic rate.
- Hormones: Thyroid hormones, in particular, significantly impact metabolism.
The Mifflin-St Jeor Equation:
This equation is widely recommended for its accuracy:
- 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
What to do with your BMR:
Your BMR is just one part of your total daily energy expenditure (TDEE). To estimate your TDEE, you need to multiply your BMR by an activity factor that reflects your lifestyle:
- Sedentary: Little to no exercise (BMR x 1.2)
- Lightly active: Exercise 1-3 days/week (BMR x 1.375)
- Moderately active: Exercise 3-5 days/week (BMR x 1.55)
- Very active: Exercise 6-7 days/week (BMR x 1.725)
- Extra active: Very intense exercise daily, or physical job (BMR x 1.9)
Your TDEE represents the total calories you burn in a day. To lose weight, you typically aim to consume fewer calories than your TDEE. To gain weight, you consume more. For maintenance, you aim to match your TDEE.