BMR Calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to stay alive — powering your heartbeat, breathing, brain activity, body temperature, and cell repair while you do nothing at all. For most people, BMR accounts for roughly 60–70% of total daily calories burned, which makes it the single most important number to know before planning any diet.
What BMR Tells You
Resting Calorie Floor
A Diet Starting Point
A Way to Track Change
How to Calculate Your BMR
Enter Your Body Stats
Type in your weight, height, and age, then select your gender. Switch between Metric (kg, cm) and Imperial (lbs, ft/in) with the unit toggle — the tool converts automatically.
Add Body Fat % (Optional)
If you know your body fat percentage, enter it to unlock the Katch-McArdle formula. It bases BMR on lean body mass, which is often more accurate for lean or very muscular people.
Read the Comparison Table
Your headline BMR uses Mifflin-St Jeor. The comparison table shows all three formulas at once so you can see how much they differ for your stats.
Move On to Daily Calories
BMR is only the resting baseline. To get your full daily calorie needs including exercise, use the TDEE Calculator tab, which builds on this BMR.
The Three BMR Formulas
No formula measures your metabolism directly — they are statistical estimates built from population studies. Each works slightly differently, which is why comparing them is useful.
| Formula | Based On | Best For |
|---|---|---|
| Mifflin-St Jeor | Weight, height, age, gender | Recommended default |
| Harris-Benedict (Revised) | Weight, height, age, gender | Classic comparison |
| Katch-McArdle | Lean body mass (body fat %) | Lean / athletic |
Mifflin-St Jeor
Published in 1990, this is the formula most dietitians use today because it tends to track real-world resting energy more closely than older equations. It is the default headline result in this tool.
Men: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161Harris-Benedict (Revised)
One of the oldest BMR equations, revised in 1984. It is widely cited and useful as a reference point, though it can slightly overestimate for some people compared with Mifflin-St Jeor.
Men: 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
Women: 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)Katch-McArdle
This formula ignores height, age, and gender and looks only at lean body mass. Because muscle drives resting metabolism, it can be the most accurate option — but only if you know your body fat percentage accurately.
Lean Body Mass (LBM) = weight × (1 − bodyFat% ÷ 100)
BMR = 370 + (21.6 × LBM kg)Calculator Features
Three-Formula Comparison
See Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle results in one table for a balanced view.
Optional Body Fat Input
Add a body fat percentage to enable the lean-mass-based Katch-McArdle estimate.
Metric & Imperial
Enter kg/cm or lbs/ft-in. The tool handles the conversion behind the scenes.
Private by Design
All math runs in your browser. Nothing is stored or sent to a server.
Frequently Asked Questions
What exactly is BMR?
Basal Metabolic Rate is the number of calories your body burns at complete rest to keep essential functions running — breathing, blood circulation, organ function, body temperature, and cell production. It does not include any movement, digestion, or exercise.
How is BMR different from TDEE?
BMR is calories burned at rest only. TDEE (Total Daily Energy Expenditure) is your full daily burn — BMR plus the calories from walking, working, and exercise. TDEE is calculated by multiplying BMR by an activity factor, which the TDEE Calculator tab does for you.
Which formula should I use?
For most people, Mifflin-St Jeor is the recommended choice and is widely used by health professionals. If you are lean or muscular and know your body fat percentage, Katch-McArdle can be more accurate because it accounts for lean body mass.
Do I need to enter my body fat percentage?
No, it is optional. Mifflin-St Jeor and Harris-Benedict work from your weight, height, age, and gender alone. Body fat % only unlocks the extra Katch-McArdle estimate — so leave it blank if you are unsure, since a wrong figure will skew that result.
Why do the three formulas give different numbers?
Each equation was developed from a different study population and uses slightly different math. Small differences are normal and expected. Comparing them gives you a realistic range rather than a single false-precision number.
Can I eat at my BMR to lose weight?
Eating only at your BMR is usually too aggressive, because you also burn calories through daily activity. A safer approach is to base a moderate deficit on your TDEE, not your BMR. For personalized medical or nutrition advice, consult a qualified healthcare professional or registered dietitian.
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