BMR Calculator
Calculate your Basal Metabolic Rate - the calories your body burns at rest
How to Use This BMR Calculator
- Enter your age (metabolism decreases with age)
- Select your gender (affects the calculation)
- Enter your height in your preferred units
- Enter your weight in kg or pounds
- Optionally enter body fat percentage for a more accurate Katch-McArdle result
- Click 'Calculate BMR' to see results from multiple formulas
Example: A 30-year-old male who is 5'10" (178 cm) and weighs 175 lbs (79 kg) has a BMR of approximately 1,780 calories per day using the Mifflin-St Jeor formula. This means his body burns 1,780 calories just to maintain basic functions while at complete rest.
Tip: Your BMR is your caloric floor - never eat fewer calories than your BMR for extended periods, as this can harm your metabolism and health.
Why Use a BMR Calculator?
Understanding your BMR is the foundation of any nutrition or weight management plan. It tells you the minimum calories your body needs to function.
- Setting a safe minimum calorie intake during weight loss
- Understanding why you burn calories even while sleeping
- Calculating Total Daily Energy Expenditure (TDEE) by adding activity
- Comparing your metabolism to population averages for your age/gender
- Identifying if your metabolism might be slower than expected (consult doctor)
- Optimizing nutrition timing and macros for athletic performance
Understanding Your Results
Your BMR represents the energy your body needs for breathing, circulation, brain function, and cell repair - without any physical activity.
| Result | Meaning | Action |
|---|---|---|
| Below average for age/gender | Lower Metabolism | May indicate muscle loss or thyroid issues. Consider strength training to build muscle, which increases BMR. |
| Average range | Typical Metabolism | Normal metabolic rate. Your TDEE will be BMR x 1.2 to 1.9 depending on activity level. |
| Above average | Higher Metabolism | Often seen in younger, more muscular individuals. You may need more calories to maintain weight. |
Meaning: Lower Metabolism
Action: May indicate muscle loss or thyroid issues. Consider strength training to build muscle, which increases BMR.
Meaning: Typical Metabolism
Action: Normal metabolic rate. Your TDEE will be BMR x 1.2 to 1.9 depending on activity level.
Meaning: Higher Metabolism
Action: Often seen in younger, more muscular individuals. You may need more calories to maintain weight.
Note: BMR accounts for 60-75% of daily calorie burn. Adding activity (TDEE) gives you the total calories needed to maintain current weight.
About BMR Calculator
Formula
Mifflin-St Jeor: Men: (10 x weight kg) + (6.25 x height cm) - (5 x age) + 5 | Women: (10 x weight kg) + (6.25 x height cm) - (5 x age) - 161 The Mifflin-St Jeor formula accounts for weight, height, age, and gender. Men generally have higher BMR due to greater muscle mass. Katch-McArdle uses lean mass: 370 + (21.6 x lean mass in kg).
Current Standards: Average BMR ranges: Men typically 1,600-1,800 calories/day; Women typically 1,400-1,600 calories/day. Athletes and muscular individuals often have BMR 10-20% higher than average.
Frequently Asked Questions
What's the difference between BMR and TDEE?
BMR is calories burned at complete rest - as if you laid in bed all day without moving. TDEE (Total Daily Energy Expenditure) is BMR plus all activity: walking, working, exercising, even fidgeting. TDEE is calculated by multiplying BMR by an activity factor: Sedentary (x1.2), Light activity (x1.375), Moderate (x1.55), Very active (x1.725), or Extreme (x1.9). TDEE is what you need to eat to maintain your current weight.
Why does BMR decrease with age?
BMR declines about 1-2% per decade after age 20, primarily due to loss of muscle mass (sarcopenia) and hormonal changes. A 50-year-old burns roughly 100-200 fewer calories at rest than they did at 25 with the same weight. This is why strength training becomes increasingly important with age - maintaining muscle mass helps preserve metabolic rate.
Can I increase my BMR?
Yes, primarily through building muscle mass. Each pound of muscle burns approximately 6 calories per day at rest, compared to 2 calories per pound of fat. Strength training, adequate protein intake (0.7-1g per pound of body weight), and quality sleep all support muscle maintenance and growth. Some evidence suggests high-intensity interval training temporarily boosts metabolism beyond the workout itself.
Why shouldn't I eat below my BMR?
Chronically eating below BMR triggers adaptive thermogenesis - your body slows metabolism to conserve energy, thinking it's experiencing famine. This leads to muscle loss, hormonal disruption (reduced thyroid function, testosterone, and estrogen), fatigue, and hair loss. After dieting ends, a suppressed metabolism makes weight regain more likely. Safe weight loss targets a caloric deficit between BMR and TDEE, typically 500-750 calories below TDEE.
Which BMR formula should I use?
Mifflin-St Jeor is recommended for most people and is what this calculator highlights. If you know your body fat percentage from calipers or a DEXA scan, Katch-McArdle may be more accurate since it uses lean mass. Harris-Benedict is older but still useful for comparison. Results typically vary by 100-200 calories between formulas - use them as estimates, not exact figures.