BMR Calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions. This calculator uses the Mifflin-St Jeor equation, the modern standard for estimating resting energy needs.
How it works
This calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate predictive formula for resting energy in healthy adults. For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women, the final constant is −161 instead of +5.
BMR represents the energy needed for basic life-sustaining functions like breathing, circulation, and cell production while at complete rest. To estimate total daily calorie needs (TDEE), the result is multiplied by an activity factor ranging from 1.2 (sedentary) to 1.725 (very active).
Tips
Use BMR as a baseline, not a strict target. To lose weight, eat below your TDEE; to gain, eat above it. A deficit or surplus of roughly 500 kcal/day shifts weight by about 0.5 kg per week.
Body composition matters — people with more muscle burn more at rest than the equation predicts, while higher body fat may mean it overestimates slightly. Re-check your numbers as your weight changes.
FAQ
What is the difference between BMR and TDEE?
BMR is the calories burned at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor to account for movement, exercise, and digestion.
Why does the formula need my sex?
On average, men have more lean muscle mass than women, which raises resting energy use. The equation adds 5 for males and subtracts 161 for females to reflect this difference.
How accurate is the Mifflin-St Jeor equation?
It estimates BMR within about 10% for most healthy adults, making it the preferred formula over older methods like Harris-Benedict. Individual results vary with muscle mass, genetics, and health conditions.