BMR Calculator
Find your daily calorie burn at rest. Choose from three scientific formulas and see your TDEE for different activity levels.
For general information only. Consult a qualified healthcare professional for personalised advice.
How to use BMR Calculator
The Basal Metabolic Rate (BMR) calculator estimates the number of calories your body burns at complete rest — just to keep your heart beating, lungs breathing and organs functioning. Three scientifically validated formulas are supported: Mifflin-St Jeor (most accurate for most people), Harris-Benedict (classic 1919 revision), and Katch-McArdle (ideal for athletes who know their body-fat percentage). Use BMR as the foundation for planning your nutrition and weight goals.
- Choose the BMR formula: Mifflin-St Jeor for general use, Katch-McArdle if you know your body-fat percentage.
- Select your unit system (metric kg/cm or imperial lbs/ft+in).
- Enter your gender, age, weight and height.
- For Katch-McArdle, also enter your body-fat percentage.
- Read your BMR and the TDEE table showing calorie needs at every activity level.
Your data never leaves your device — 100% private processing.
What BMR measures and why it matters
BMR is the energy your body requires to sustain life at complete rest — breathing, circulation, thermoregulation and cell repair. It accounts for roughly 60–70 % of total daily energy expenditure. Understanding your BMR lets you set a realistic calorie floor: eating below your BMR long-term is physiologically stressful and can slow metabolism. Multiply BMR by an activity factor to estimate your true daily needs (TDEE).
Mifflin-St Jeor vs Harris-Benedict vs Katch-McArdle
The 1990 Mifflin-St Jeor equation is widely regarded as the most accurate for the general population, with an average error of about 10 %. Harris-Benedict (1919, revised 1984) tends to over-estimate by 5–15 % and is now considered less accurate. Katch-McArdle bases its calculation solely on lean body mass, making it exceptionally accurate for lean athletes but requiring a reliable body-fat measurement.
| Formula | Best for | Inputs required | Typical error |
|---|---|---|---|
| Mifflin-St Jeor | General population | Gender, age, weight, height | ~10% |
| Harris-Benedict | Legacy / comparison | Gender, age, weight, height | 5–15% |
| Katch-McArdle | Athletes / lean individuals | Lean body mass (= weight × (1 − BF%)) | ~5% |
From BMR to TDEE — adding activity
To find your Total Daily Energy Expenditure, multiply your BMR by an activity multiplier: sedentary (×1.2), lightly active (×1.375), moderately active (×1.55), very active (×1.725) or extra active (×1.9). These multipliers approximate the thermic effect of exercise and non-exercise activity thermogenesis (NEAT). Most people underestimate their activity level; when in doubt, start with the lower estimate and adjust over 2–4 weeks based on real weight changes.
Glossary
- BMR
- Basal Metabolic Rate — calories burned at absolute rest for survival functions.
- TDEE
- Total Daily Energy Expenditure — BMR multiplied by an activity factor.
- Lean Body Mass
- Total body weight minus fat mass; used in the Katch-McArdle formula.
- NEAT
- Non-Exercise Activity Thermogenesis — calories burned through daily movement other than deliberate exercise.
- Mifflin-St Jeor
- The most widely validated BMR equation for the general population (1990).
Related reading
Frequently Asked Questions
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Why use BMR Calculator?
- Based on widely-accepted clinical and scientific formulas
- No personal data stored — all calculations run locally
- Supports both metric and imperial units
- Results include actionable recommendations
Common use cases
- Calculate BMI before a doctor's appointment
- Estimate daily calorie needs for a weight loss goal
- Track ideal body weight range for a fitness plan
- Calculate pregnancy due date
- Find out your recommended water intake based on body weight
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