🔥BMR Calculator
Calculate your Basal Metabolic Rate (BMR) and daily calorie needs using scientifically proven formulas. Discover how many calories your body burns at rest and with different activity levels.
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BMR Formula Comparison
| Formula | Best For | Accuracy | Notes |
|---|---|---|---|
| Mifflin-St Jeor | General population | 95% | Most accurate, recommended by nutritionists |
| Harris-Benedict | Historical reference | 90% | Older formula, slightly overestimates |
| Katch-McArdle | Lean/athletic individuals | 90% | Requires body fat percentage |
How to Use This Calculator
Calculating your Basal Metabolic Rate is quick and straightforward. Follow these steps:
- Choose your unit system -- toggle between Metric (kg/cm) and Imperial (lbs/inches) using the button at the top.
- Enter your personal information -- provide your gender, age, weight, and height in the form fields.
- Select a BMR formula -- pick from Mifflin-St Jeor (recommended), Harris-Benedict (revised), or Katch-McArdle (for lean individuals).
- View your results -- your BMR and daily calorie needs at five different activity levels are calculated automatically as you type.
- Apply the numbers -- use your BMR and activity-adjusted calories to plan your nutrition for weight loss, maintenance, or gain.
Understanding Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate is the minimum number of calories your body requires to perform its most basic life-sustaining functions while at complete rest. These functions include breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature. BMR typically accounts for 60-75% of the total calories you burn each day, making it the largest component of your daily energy expenditure.
Harris-Benedict vs. Mifflin-St Jeor Equations
The Harris-Benedict equation was first published in 1919 and revised in 1984. For decades it was the standard method for estimating BMR. However, research published in the Journal of the American Dietetic Association found that the Mifflin-St Jeor equation (developed in 1990) provides a more accurate estimate for the modern population, within approximately 5% of values measured by indirect calorimetry. The Katch-McArdle formula is a third option that uses lean body mass instead of total weight, making it particularly useful for individuals with known body fat percentages and athletic builds.
Mifflin-St Jeor (Recommended):
Male: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
Female: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
Harris-Benedict (Revised 1984):
Male: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age)
Female: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age)
Katch-McArdle:
BMR = 370 + (21.6 x lean body mass in kg)
Factors That Affect BMR
Several factors influence your Basal Metabolic Rate. Age is one of the most significant -- BMR decreases by roughly 1-2% per decade after age 20 as muscle mass naturally declines. Gender plays a role because men typically carry more muscle mass, which is metabolically more active than fat tissue. Taller and heavier individuals generally have higher BMRs because there is more tissue to maintain. Genetics, hormonal balance (particularly thyroid function), and body composition also have meaningful impacts on your metabolic rate.
Why BMR Matters
Knowing your BMR is essential for any nutrition or fitness plan. Consuming fewer calories than your BMR for prolonged periods can slow your metabolism, cause muscle loss, and lead to nutrient deficiencies. A well-designed calorie plan ensures you never drop below your BMR, using activity-level adjustments to create a safe and sustainable caloric deficit for weight loss or surplus for muscle gain.
Worked Example
Consider a 28-year-old female who weighs 65 kg and stands 165 cm tall, using the Mifflin-St Jeor equation:
BMR = (10 x 65) + (6.25 x 165) - (5 x 28) - 161
BMR = 650 + 1031.25 - 140 - 161
BMR = 1,380 calories/day
With moderate activity (multiplier 1.55):
Daily calories = 1,380 x 1.55 = 2,139 calories/day
Average BMR Ranges by Age and Gender
The following table shows typical BMR ranges for adults at average weight and height. Individual results will vary based on body composition and other factors.
| Age Range | Male BMR (cal/day) | Female BMR (cal/day) |
|---|---|---|
| 18-25 | 1,600 - 1,800 | 1,300 - 1,500 |
| 26-35 | 1,550 - 1,750 | 1,250 - 1,450 |
| 36-45 | 1,500 - 1,700 | 1,200 - 1,400 |
| 46-55 | 1,450 - 1,650 | 1,150 - 1,350 |
| 56-65 | 1,400 - 1,600 | 1,100 - 1,300 |
| 65+ | 1,300 - 1,500 | 1,050 - 1,250 |
Understanding TDEE: Total Daily Energy Expenditure
Your BMR tells you how many calories your body burns at rest. To find your total daily calorie needs, you multiply BMR by an activity factor. This gives you your TDEE, the actual number of calories you burn in a full day including all physical activity and daily movement.
| Activity Level | Multiplier | Description | Example (BMR 1,600) |
|---|---|---|---|
| Sedentary | 1.2 | Desk job, no exercise | 1,920 cal |
| Lightly Active | 1.375 | Light exercise 1-3 days/week | 2,200 cal |
| Moderately Active | 1.55 | Moderate exercise 3-5 days/week | 2,480 cal |
| Very Active | 1.725 | Hard exercise 6-7 days/week | 2,760 cal |
| Extra Active | 1.9 | Athlete or physical job + training | 3,040 cal |
Evidence-Based Ways to Boost Your Metabolism
While your BMR is largely determined by genetics, age, and body composition, research shows several strategies can meaningfully increase your metabolic rate over time.
Build Lean Muscle
Each pound of muscle burns approximately 6 calories per day at rest, compared to 2 calories per pound of fat. Strength training 2-3 times per week can add 3-5 lbs of muscle in 3-6 months.
High-Intensity Exercise
HIIT (High-Intensity Interval Training) raises your metabolic rate for 24-48 hours after exercise through excess post-exercise oxygen consumption (EPOC).
Protein Intake
Protein has the highest thermic effect of food (TEF) at 20-30%, meaning your body burns 20-30% of protein calories just digesting them. Aim for 0.8-1g per pound of body weight.
Sleep Quality
Poor sleep (less than 7 hours) can reduce BMR by 2-8%. Chronic sleep deprivation disrupts leptin and ghrelin hormones, increasing appetite and reducing metabolic rate.
Stay Hydrated
Drinking 500ml of cold water can temporarily boost metabolism by 24-30% for about 60-90 minutes. Aim for 8-10 glasses daily.
Avoid Crash Diets
Severely restricting calories (below BMR) triggers adaptive thermogenesis, where your body reduces metabolic rate by 15-25% to conserve energy. Always eat above your BMR.
Important Disclaimer
BMR calculations are based on statistical models derived from population-level studies and provide estimates, not exact measurements. Your actual metabolic rate can be influenced by genetics, hormonal conditions (such as hypothyroidism or hyperthyroidism), medications, stress levels, sleep quality, and body composition. These results are intended for general educational and informational purposes only. They do not constitute medical advice. Before making any significant dietary changes or starting a new fitness program, consult with a qualified healthcare professional or registered dietitian, particularly if you have any underlying health conditions.