Your basal metabolism is the energy your body uses at rest to keep you alive: breathing, circulation, cell repair, hormone balance, and more. Use the calculator below to estimate your daily basal metabolic rate (BMR) and your total daily calorie needs based on activity level.
What is basal metabolism?
Basal metabolism refers to the minimum energy your body needs to perform essential functions while at complete rest. This is commonly reported as BMR (Basal Metabolic Rate), usually measured in calories per day.
Even if you stay in bed all day, your body still burns calories for:
- Breathing and oxygen transport
- Heart and brain function
- Body temperature regulation
- Cell turnover and tissue repair
- Hormone production
How this calculator works
This calculator uses the Mifflin-St Jeor equation, one of the most widely used formulas for estimating BMR in adults.
Mifflin-St Jeor equations
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
After BMR is estimated, your activity multiplier is applied to estimate TDEE (Total Daily Energy Expenditure)—your approximate maintenance calories.
How to use your result
1) Maintenance
If you want to maintain your current weight, aim near your TDEE value over time.
2) Fat loss
For gradual fat loss, many people use a deficit of about 300-500 calories below TDEE per day, combined with adequate protein and resistance training.
3) Muscle gain
For lean mass gain, a modest surplus of 150-300 calories above TDEE may help, while focusing on progressive overload in training and recovery quality.
What influences basal metabolic rate?
- Body composition: More lean mass generally means higher BMR.
- Age: BMR tends to decline with age, partly due to muscle loss.
- Sex: Average differences in lean mass affect expected BMR values.
- Genetics: Individuals naturally vary in metabolic efficiency.
- Hormonal health: Thyroid and other endocrine factors can shift metabolism.
- Energy intake history: Prolonged aggressive dieting can temporarily reduce expenditure.
Important note
This tool gives an estimate, not a diagnosis. Real-world calorie needs vary day to day. Use your result as a starting point, then adjust based on 2-4 weeks of body-weight trend, performance, hunger, and recovery.