BMR Calculator
Calculate your Basal Metabolic Rate and see your TDEE across every activity level
What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, cell production, and temperature regulation. It accounts for approximately 60-75% of your total daily energy expenditure, with the remainder coming from physical activity and digestion.
BMR Formulas Used
Mifflin-St Jeor (Male): BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Mifflin-St Jeor (Female): BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Katch-McArdle (if body fat % entered): BMR = 370 + 21.6 × Lean Body Mass(kg)
TDEE: BMR × Activity Multiplier
How to Use This Calculator
- Enter your age, gender, weight, and height (switch units in Advanced Options if needed).
- Select the activity level that best matches your typical week.
- Optionally enter your body fat percentage for the more precise Katch-McArdle formula.
- Click "Calculate" to see your BMR, TDEE, and calorie targets — plus how TDEE changes across every activity level.
Understanding Your Results
BMR (Basal Metabolic Rate)
Calories your body needs at complete rest to maintain basic bodily functions.
TDEE (Total Daily Energy Expenditure)
Total calories burned daily, including BMR, physical activity, and digestion.
For Weight Loss
Eat 250-500 calories below TDEE for gradual, sustainable weight loss.
For Weight Gain
Eat 250-500 calories above TDEE for steady, mostly lean weight gain.
Why Activity Level Matters So Much
Because TDEE is simply BMR multiplied by an activity factor, the gap between Sedentary (1.2×) and Extra Active (1.9×) can mean over 1,000 extra calories per day for the exact same body. The comparison table on this page shows your personal TDEE at every activity level side by side, so you can see the real impact of becoming more or less active without recalculating manually.
Tips to Support a Healthy Metabolism
- Include resistance training to build and preserve muscle, which raises BMR.
- Eat adequate protein, especially during a calorie deficit.
- Avoid prolonged very-low-calorie diets that can slow metabolism over time.
- Recalculate your BMR whenever your weight changes meaningfully.
Advantages of Using This Calculator
- Shows TDEE across all five activity levels in one table — no repeated recalculating.
- Supports the more precise Katch-McArdle formula when body fat % is known.
- Works in metric or imperial units.
- Visualizes how much of your daily burn comes from rest versus activity.
Limitations
- Formulas are population averages; individual metabolism can vary by 5-10% or more.
- Does not account for medical conditions, medications, or hormonal factors.
- Activity level is a rough weekly average, not a day-by-day measurement.
Common Mistakes to Avoid
- Selecting an activity level well above your actual typical week.
- Eating close to or below BMR itself, rather than below TDEE.
- Not recalculating after a meaningful weight change.
- Stacking a separate fitness-tracker calorie count on top of an already-active activity level.
Worked Examples
Sedentary Office Worker
Profile: Male, 32 years, 82 kg, 178 cm
Activity Level: Sedentary (little or no exercise)
BMR: 1,779 cal/day
TDEE: 2,135 cal/day
Even with a solid BMR, a sedentary lifestyle keeps total daily needs relatively modest — a common trap for people who eat as if they were more active.
Lightly Active Woman
Profile: Female, 29 years, 62 kg, 163 cm
Activity Level: Lightly Active (1-3 days/week)
BMR: 1,323 cal/day
TDEE: 1,819 cal/day
Light exercise a few times a week adds a modest but meaningful boost over BMR alone.
Moderately Active Man
Profile: Male, 45 years, 88 kg, 176 cm
Activity Level: Moderately Active (3-5 days/week)
BMR: 1,749 cal/day
TDEE: 2,711 cal/day
Regular exercise several days a week pushes total daily needs well above resting metabolism.
Very Active Younger Woman
Profile: Female, 24 years, 58 kg, 168 cm
Activity Level: Very Active (6-7 days/week)
BMR: 1,368 cal/day
TDEE: 2,360 cal/day
Near-daily training substantially raises TDEE relative to BMR, even for a smaller body frame.
Frequently Asked Questions
What exactly is BMR?
Basal Metabolic Rate is the number of calories your body needs to perform basic life-sustaining functions — breathing, circulation, cell production, and temperature regulation — while at complete rest. It typically accounts for 60-75% of total daily calorie burn.
How is BMR different from TDEE?
BMR only measures calories burned at rest, while TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor to estimate the calories you actually burn in a full day, including movement, exercise, and digestion.
Which formula does this calculator use?
By default it uses the Mifflin-St Jeor equation, widely regarded as the most accurate general-population formula. If you enter your body fat percentage in Advanced Options, it switches to the Katch-McArdle formula, which uses lean body mass and can be more precise if you know your body composition.
Why does the same BMR produce such different TDEE numbers?
TDEE is BMR multiplied by an activity factor ranging from 1.2 (Sedentary) to 1.9 (Extra Active), so the same resting metabolism can translate into a swing of 1,000+ calories per day depending purely on how active your lifestyle is. The comparison table below shows your BMR at every activity level side by side.
What factors affect BMR besides age, weight, and height?
Muscle mass, genetics, hormone levels (especially thyroid function), and even climate can influence BMR. Two people with identical age, weight, and height can still have noticeably different metabolic rates.
Can I increase my BMR?
Building muscle through resistance training tends to raise BMR since muscle tissue burns more calories at rest than fat tissue. Eating enough protein and avoiding prolonged, very low-calorie dieting also help preserve — and can support — a higher metabolic rate.
Does BMR decrease with age?
Yes — BMR gradually declines with age, partly due to natural loss of muscle mass over time, which is why calorie needs typically decrease somewhat in later adulthood even at the same activity level.
How many calories should I eat to lose weight based on my BMR?
Rather than eating at or below BMR, most guidance suggests eating below your TDEE (BMR × activity) by 250-500 calories for sustainable weight loss, since BMR alone does not include the calories burned through daily activity.
Is it dangerous to eat below my BMR?
Consistently eating below BMR for extended periods can slow metabolism, increase muscle loss, and affect hormone regulation, so it is generally not recommended without medical supervision. Weight loss targets should typically stay above BMR, with the deficit coming from the gap between TDEE and BMR.
What is the Katch-McArdle formula and when should I use it?
Katch-McArdle calculates BMR from lean body mass rather than total weight, using the formula 370 + 21.6 × lean mass (kg). It tends to be more accurate for people who are leaner or more muscular than average and who know their approximate body fat percentage.
Can I use pounds and inches instead of kilograms and centimeters?
Yes — Advanced Options lets you switch to pounds for weight and inches for height, and the calculator converts everything internally so results stay accurate regardless of which units you use.
How often should I recalculate my BMR?
Recalculate whenever your weight changes meaningfully (a few kilograms/pounds) or every 4-6 weeks during an active weight loss or gain phase, since BMR shifts as body weight and composition change.
Conclusion
Your BMR is the foundation of every calorie decision you make — it tells you what your body needs at rest before activity is even considered. Use this calculator to find your BMR and TDEE, compare how activity level changes your numbers, and set a realistic calorie target for your goal.