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.
Worked examples
Woman, 65 kg, 165 cm, 30 yrs
Inputs: Mifflin-St Jeor, female
Result: 10×65 + 6.25×165 − 5×30 − 161 = 1,370 kcal/day BMR
Man, 80 kg, 180 cm, 35 yrs
Inputs: Mifflin-St Jeor, male
Result: 10×80 + 6.25×180 − 5×35 + 5 = 1,755 kcal/day BMR
From BMR to TDEE
Inputs: BMR 1,755 × 1.55 (moderately active)
Result: ≈ 2,720 kcal/day total expenditure
TDEE for a 1,600 kcal BMR by activity level
| Activity level | Multiplier | Daily calories |
|---|---|---|
| Sedentary | ×1.2 | 1,920 kcal |
| Lightly active | ×1.375 | 2,200 kcal |
| Moderately active | ×1.55 | 2,480 kcal |
| Very active | ×1.725 | 2,760 kcal |
| Extra active | ×1.9 | 3,040 kcal |
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
Why use BMR Calculator?
- Estimate your resting calorie floor using three validated formulas including Mifflin-St Jeor
- Switch to Katch-McArdle for lean-mass-based accuracy if you track body-fat percentage
- View a TDEE table across all five activity levels from a single BMR calculation
- Understand the minimum calories your body requires before adding any goal adjustment
Common use cases
- Set a safe calorie floor before designing a weight-loss plan with a registered dietitian
- Compare Mifflin-St Jeor and Harris-Benedict outputs to see how formula choice shifts your target
- Use Katch-McArdle after measuring body fat with calipers for a lean-mass-adjusted BMR
- Calculate resting calorie burn as the foundation for building a protein and macro split
- Check whether your current daily intake is above or below your bare resting metabolic need
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