BMR Calculator: Basal Metabolic Rate and Daily Calorie Needs
Your basal metabolic rate is the energy your body burns at complete rest, just keeping organs, temperature and cells running. It typically accounts for 60-70% of total daily calorie use, which makes it the foundation of any calorie target for losing, maintaining or gaining weight.
How BMR is estimated
The Mifflin-St Jeor equation is the current standard and is generally more accurate than the older Harris-Benedict formula. It uses weight, height, age and sex: metabolic rate falls with age and rises with lean body mass, which is why two people at the same weight can differ by several hundred calories a day.
From BMR to TDEE
- Sedentary (desk job, little exercise): BMR × 1.2
- Lightly active (1-3 sessions a week): BMR × 1.375
- Moderately active (3-5 sessions): BMR × 1.55
- Very active (6-7 sessions): BMR × 1.725
- Athlete or physical job: BMR × 1.9
Using the number safely
Total daily energy expenditure is your maintenance level. A deficit of roughly 500 calories a day tends to produce about 0.5 kg of loss per week. Eating below your BMR for long periods is not recommended: it makes adequate protein and micronutrient intake difficult and accelerates loss of lean tissue. Any equation is an estimate — track real weight change over two to three weeks and adjust from there.
Key takeaways — BMR Calculator
- BMR is resting energy use; TDEE is BMR multiplied by an activity factor.
- Preserve muscle with adequate protein and resistance training while in a deficit.
- Verify the estimate against actual weight trends, not daily fluctuations.