Basal Metabolic Rate (BMR) Calculator

What is the Basal Metabolic Rate (BMR) Calculator?

The BMR Calculator estimates the minimum number of calories your body needs to sustain essential functions while at complete rest — including breathing, blood circulation, temperature regulation, and cell production. It uses the widely trusted Mifflin-St Jeor equation and takes your weight, height, age, and biological sex as inputs to deliver a personalised calorie baseline in kcal/day.

How to Use This Calculator

Enter your body weight in kilograms, your height in centimeters, and your age in years, then select your biological sex. The calculator instantly applies the Mifflin-St Jeor formula and returns your BMR in kilocalories per day. For best accuracy, use measured values rather than estimates. Once you have your BMR, multiply it by your activity level to find your Total Daily Energy Expenditure (TDEE).

Formula Explained

This calculator uses the Mifflin-St Jeor Equation, considered the most accurate BMR formula for most adults. The formula is: Males: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 and Females: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. For example, a 35-year-old male weighing 90.7 kg and standing 183 cm tall would have a BMR of approximately 1,882 kcal/day — the energy his body burns at full rest.

Interpret Your Results

Your BMR result tells you the absolute minimum calories your body needs to survive at rest — it does not include calories for daily movement or exercise. A BMR result alone is not a target intake; it is the foundation for calculating TDEE. Results vary widely between individuals based on body size, muscle mass, age, and sex, so there is no single 'normal' BMR value.

Expert Tips

1. Never eat below your BMR — doing so deprives vital organs of fuel. 2. Build muscle through resistance training to naturally raise your BMR over time. 3. Avoid crash diets — prolonged calorie restriction lowers your BMR and makes future weight loss harder. 4. Recalculate regularly — your BMR changes as your weight, age, and muscle mass shift. 5. Use BMR as a starting point, not a daily calorie target — always factor in your activity level to get your true energy needs.

Conclusion

Understanding your Basal Metabolic Rate is the essential first step in managing your nutrition and achieving your health goals. Use your BMR result alongside an activity multiplier to determine how many calories you truly need each day, and consult a registered dietitian for personalised guidance.