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BMR Calculator.
Calculate your Basal Metabolic Rate (BMR) using Mifflin-St Jeor, Revised Harris-Benedict, and Katch-McArdle formulas.
Set your values
Results update as you type.
Required for Katch-McArdle formula to determine lean body mass.
Your Basal Metabolic Rate (BMR)
This is the number of calories your body needs to survive at absolute rest, without any activity or digestion.
Compare BMR Formulas
Mifflin-St Jeor
1674 kcal
Revised Harris-Benedict
1724 kcal
Katch-McArdle
N/A
Daily Calorie Intake by Activity Level (TDEE)
| Activity Level | Calories |
|---|---|
| SedentaryLittle or no exercise | 2009 kcal |
| Lightly ActiveLight exercise 1-3 days/week | 2302 kcal |
| Moderately ActiveModerate exercise 3-5 days/week | 2595 kcal |
| Very ActiveHard exercise 6-7 days/week | 2888 kcal |
| Extremely ActiveHard daily exercise & physical job | 3181 kcal |
FAQs
What is Basal Metabolic Rate (BMR)?
BMR is the minimum number of calories your body needs to maintain basic life-sustaining functions (like breathing and circulation) at complete rest.
Which BMR formula is the most accurate?
The Mifflin-St Jeor equation is widely considered the most accurate for modern lifestyles. If you know your body fat percentage, the Katch-McArdle formula is highly recommended as it accounts for lean muscle mass.
What is the difference between BMR and RMR?
BMR (Basal Metabolic Rate) is measured under strict laboratory conditions at rest. RMR (Resting Metabolic Rate) is measured under less restrictive conditions and is slightly higher but close enough for daily planning.
How does BMR help with weight loss?
Your BMR is the foundation of your daily calorie expenditure. By adding your activity level, you get your Total Daily Energy Expenditure (TDEE). Eating below your TDEE creates a calorie deficit for weight loss.
How to Use the BMR Calculator
Estimate your Basal Metabolic Rate — the calories your body burns at complete rest.
- Enter your age, sex, height, and weight.
- See your BMR in calories per day.
- Multiply by an activity factor to get total daily needs (TDEE).
BMR Formula (Mifflin-St Jeor)
Men
The most widely used modern BMR estimate.
Example:
Input: 80kg, 180cm, 30y
Calculation: 800 + 1125 − 150 + 5
Result: 1,780 kcal/day
Women
Same formula with a different constant.
Example:
Input: 65kg, 165cm, 30y
Calculation: 650 + 1031 − 150 − 161
Result: 1,370 kcal/day
Real-World Use Cases
Calorie Targets
Set a baseline before adding activity.
Weight Management
Eat below TDEE to lose, above to gain.
Tips
Tips
- BMR is rest-only; TDEE adds activity.
- Muscle mass raises BMR, which is why strength training helps.
Related Calculators
Cite this calculator
Canonical URL: https://mathify.one/en/fitness/bmr
Cite as: Mathify. (2026). BMR Calculator. https://mathify.one/en/fitness/bmr
Use Cases
Weight Management Planning
Determine your resting calorie burn to set realistic calorie targets for weight loss, gain, or maintenance.
Example: If your BMR is 1,500 calories, you might aim for 1,200–1,300 calories daily to lose weight.
Nutrition and Fitness Tracking
Use BMR as a baseline to calculate total daily energy expenditure (TDEE) and adjust macronutrient intake.
Example: Combine BMR with activity level to estimate daily calorie needs for training.
Frequently Asked Questions
- What is BMR and why is it important?
- BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions like breathing and circulation. It forms the baseline for daily calorie needs, helping you manage weight or plan nutrition.
- Which BMR formula is most accurate?
- The Mifflin-St Jeor equation is widely considered the most accurate for the general population. The Revised Harris-Benedict is also reliable, while Katch-McArdle is best for lean individuals if you know your body fat percentage.
- How does body fat percentage affect BMR?
- Muscle tissue burns more calories than fat, so a lower body fat percentage (more muscle) typically increases BMR. The Katch-McArdle formula uses body fat to estimate lean mass, making it more precise for athletic or muscular individuals.
Tips & Common Mistakes
Tips
- Enter your height in either centimeters or feet/inches – the calculator will handle the conversion.
- For the Katch-McArdle formula, provide an accurate body fat percentage for the best estimate.
- Use the same formula consistently when tracking changes over time to see trends.
- BMR is a resting estimate; multiply by an activity factor to estimate total daily burn.
Common Mistakes to Avoid
- Using the wrong height unit – double-check if you entered cm or ft/in.
- Forgetting to enter body fat percentage when using Katch-McArdle, which then may not be accurate.
- Assuming BMR equals total daily calorie needs – it's only the resting portion.
Last updated: August 13, 2026