What This Calculator Estimates
Basal Metabolic Rate (BMR) estimates the number of calories your body burns at complete rest just to maintain basic functions like breathing, circulation, and cell production, typically calculated using formulas based on weight, height, age, and sex (such as the Mifflin-St Jeor or Harris-Benedict equations). BMR serves as the foundation for estimating total daily calorie needs once activity level is factored in, which is why it's often paired with a TDEE (Total Daily Energy Expenditure) calculation.
How to Use This Calculator
- Enter age, sex, height, and weight.
- Use current measurements for the most relevant estimate.
- Click Calculate BMR to view the result.
- Review the estimated resting calories per day.
- Use the estimate with other planning tools if needed.
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Tips for a More Accurate Estimate
- Use BMR alongside a TDEE calculator to estimate your true total daily calorie needs.
- Remember BMR formulas are estimates — actual metabolic rate varies by individual factors like muscle mass.
- Recalculate BMR periodically as your weight, age, or body composition changes.
- Consider that maintaining muscle mass through strength training can help support a higher BMR over time.
- Don't rely on BMR alone for calorie planning — factor in activity level for a complete picture.
Frequently Asked Questions
What does BMR actually measure?
BMR estimates the calories your body burns at complete rest to maintain basic life functions, not including any calories burned through movement, digestion, or exercise.
What factors affect BMR the most?
Weight, height, age, and sex are the primary inputs in standard BMR formulas, with muscle mass also playing a significant role since muscle burns more calories at rest than fat tissue.
Is BMR the same as TDEE?
No, BMR is your calorie burn at complete rest, while TDEE (Total Daily Energy Expenditure) adds your activity level on top of BMR to estimate total daily calorie needs.
Why does BMR decrease with age?
BMR typically declines with age partly due to natural loss of muscle mass over time, which is one reason maintaining strength training becomes increasingly valuable as people get older.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is generally considered more accurate for most modern populations compared to the older Harris-Benedict equation, though individual variation means any formula is an estimate.
This calculator provides informational health estimates only and is not medical advice. Individual calorie needs can vary for many reasons.
Last updated: May 11, 2026