Basal Metabolic Rate (BMR) Calculator
Understanding Your Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform basic, life-sustaining functions while at rest. Even when you are sleeping or sitting perfectly still, your body is burning energy to support breathing, circulation, nutrient processing, and cell production. Understanding your BMR is the foundation for any successful weight management or fitness plan.
How is BMR Calculated?
This calculator uses the Mifflin-St Jeor Equation, which is currently considered the most accurate standard for estimating metabolic rate. The formula takes into account your gender, weight, height, and age to determine how much energy your internal organs require to function.
- 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
BMR vs. TDEE: What is the Difference?
While BMR represents your energy expenditure at complete rest, your Total Daily Energy Expenditure (TDEE) accounts for your physical activity throughout the day. To find your maintenance calories, you multiply your BMR by an activity factor:
- Sedentary: BMR x 1.2 (Office job, little exercise)
- Lightly Active: BMR x 1.375 (Light exercise 1-3 days a week)
- Moderately Active: BMR x 1.55 (Moderate exercise 3-5 days a week)
- Very Active: BMR x 1.725 (Hard exercise 6-7 days a week)
Factors That Influence Your Metabolic Rate
Several variables can cause your BMR to fluctuate, including:
- Muscle Mass: Muscle tissue burns more calories than fat tissue, even at rest. Increasing your lean muscle mass will naturally raise your BMR.
- Age: As we get older, we typically lose muscle mass and metabolic processes slow down, leading to a lower BMR.
- Genetics: Some people naturally have a faster metabolism due to hereditary factors.
- Hormones: Thyroid function and other hormonal balances play a significant role in how quickly your body burns energy.
Realistic Example Calculation
Consider a 35-year-old male who weighs 80kg and is 180cm tall. Using the Mifflin-St Jeor formula:
(10 × 80) + (6.25 × 180) – (5 × 35) + 5 = 800 + 1125 – 175 + 5 = 1,755 Calories.
If this individual has a sedentary job, his total daily needs would be approximately 2,106 calories (1,755 x 1.2). To lose weight safely, he might aim for a daily intake of 1,600 to 1,800 calories.
Using BMR for Weight Loss or Gain
Once you know your BMR and TDEE, you can control your weight with precision. To lose weight, you must create a caloric deficit (consume fewer calories than your TDEE). To gain muscle or weight, you must create a caloric surplus. Experts generally recommend a deficit of 500 calories per day to lose approximately 1 pound (0.5 kg) per week safely.