BMR Calculator
Calculate Basal Metabolic Rate — calories your body burns at rest per day.
BMR Calculator
Calculate Basal Metabolic Rate — calories your body burns at rest per day.
Basal Metabolic Rate — Mifflin-St Jeor Equation
ℹ️ Multiply BMR by activity factor: Sedentary ×1.2 | Light ×1.375 | Moderate ×1.55 | Very active ×1.725 | Extra active ×1.9
Disclaimer
Results provided by this calculator are for informational and educational purposes only. They are based on the values you enter and standard formulas, and should not be considered financial, medical, legal, or professional advice. Always consult a qualified professional before making important decisions based on these results. Roughtools makes no warranties regarding the accuracy or completeness of these calculations for your specific situation.
Frequently Asked Questions
Pro Tips
The Mifflin-St Jeor equation used here is the most validated for most adults. But BMR estimates can be off by 10-15% — actual calorie needs require tracking and adjustment.
A calorie deficit of 500/day theoretically produces 1 lb/week of fat loss, but metabolic adaptation slows this over time. Break plateaus with diet breaks and strength training.
Protein has the highest thermic effect of food (20-35% of calories burned digesting it) and preserves muscle during weight loss. Prioritise it to protect your BMR.
Exercise activity is often overestimated. Most fitness apps overcalculate calorie burn. Focus on non-exercise activity thermogenesis (NEAT) — walking, fidgeting, daily movement.
When to Use This Calculator
Calculate your TDEE (BMR × activity) to know your calorie maintenance level before creating a deficit.
Find your calorie maintenance level to add a 200–300 calorie surplus for lean muscle gain.
Adjust calorie needs upward for marathon training or other high-intensity programs where TDEE increases dramatically.
Get a starting calorie target to enter into a food tracking app. Adjust up or down after 2–3 weeks based on results.
Calculate calorie needs during recovery periods when activity level changes, ensuring adequate nutrition for healing.
About the BMR Calculator
This BMR calculator computes your Basal Metabolic Rate using the three most widely validated equations — Mifflin-St Jeor (most accurate for general use), Harris-Benedict (revised), and Katch-McArdle (most accurate when you know your lean mass). BMR is the minimum calories your body needs to sustain vital functions at complete rest, forming the foundation for all calorie-based planning. Results apply to adults 18+ only.
How to Use the BMR Calculator
- 1
Select your sex and enter your age in years.
- 2
Enter your height and weight in metric or imperial units.
- 3
Optionally enter lean body mass (kg) if known — enables the Katch-McArdle formula.
- 4
See BMR values from all three formulas side by side.
- 5
Use the recommended value (Mifflin-St Jeor) as input for your TDEE calculation.
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