BMR Calculator
Calculate your Basal Metabolic Rate (BMR) and daily calorie requirements across five activity levels using the Mifflin-St Jeor, Revised Harris-Benedict, or Katch-McArdle equations.
Your BMR Results
Your Basal Metabolic Rate (BMR)
1,730 Calories/day
Daily Calorie Needs Based on Activity Level
Multiply your baseline BMR by your typical weekly physical activity to estimate your Total Daily Energy Expenditure (TDEE):
| Activity Level | Calories / Day |
|---|---|
| Sedentary Little or no exercise (BMR × 1.2) | 2,076 |
| Light Exercise Light exercise 1–3 days/week (BMR × 1.375) | 2,379 |
| Moderate Exercise Moderate exercise 3–5 days/week (BMR × 1.55) | 2,682 |
| Active Hard exercise 6–7 days/week (BMR × 1.725) | 2,984 |
| Very Active Intense daily exercise or physical job (BMR × 1.9) | 3,287 |
Note on Exercise Intensity:
• Exercise: 15–30 minutes of elevated heart rate activity.
• Intense Exercise: 45–120 minutes of sustained elevated heart rate activity.
All figures above are scientific estimates for educational reference and do not substitute clinical metabolic testing.
What Is BMR?
Basal Metabolic Rate (BMR) is the minimum amount of energy your body requires over a 24-hour window to keep vital physiological systems functioning while at complete physical and digestive rest. Even if you stayed in bed all day without moving a muscle, your body would still burn a substantial number of calories to sustain life.
Your baseline metabolic rate powers autonomic processes including breathing, blood circulation, heart contractions, brain and nerve signaling, kidney filtration, cell regeneration, and core temperature regulation. For most people, BMR accounts for 60% to 75% of total daily calorie expenditure—making it the single largest component of human metabolism.
How Does the BMR Calculator Work?
This BMR Calculator evaluates your physical biometrics—age, biological sex, height, and weight (plus optional body fat percentage)—and processes them through peer-reviewed clinical equations. When you enter US units (feet, inches, and pounds), the calculator converts your measurements to precise metric equivalents (centimeters and kilograms) behind the scenes before applying your chosen metabolic formula.
Once your baseline BMR is established, the calculator applies standard activity multipliers to estimate your daily maintenance energy needs across five lifestyle tiers, allowing you to view results in either Calories (kcal) or Kilojoules (kJ) (where 1 kcal = 4.184 kJ).
BMR Formulas Explained
Over the past century, exercise physiologists and clinical nutritionists have developed several predictive equations to estimate Basal Metabolic Rate without requiring expensive laboratory gas-exchange equipment. Our calculator supports the three most trusted formulas:
1. Mifflin-St Jeor Equation (Default & Most Accurate for General Adults)
Introduced by MD Mifflin and ST St Jeor in 1990, this formula is endorsed by the Academy of Nutrition and Dietetics as the gold-standard equation for estimating BMR in healthy adults when body fat percentage is unknown.
For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
2. Revised Harris-Benedict Equation
Originally published in 1918 and revised by Roza and Shizgal in 1984 using modern anthropometric data, the Revised Harris-Benedict equation remains widely referenced in clinical literature and fitness coaching.
For Men: BMR = (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years) + 88.362
For Women: BMR = (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years) + 447.593
3. Katch-McArdle Formula
Unlike the Mifflin-St Jeor and Harris-Benedict formulas, the Katch-McArdle equation calculates BMR exclusively from Lean Body Mass (LBM). Because skeletal muscle and organs drive metabolic rate regardless of sex or stature, Katch-McArdle is especially helpful for resistance-trained athletes and lean individuals who know their body fat percentage.
Lean Body Mass (kg): LBM = weight in kg × (1 − [body fat % / 100])
BMR (Men & Women): BMR = 370 + (21.6 × Lean Body Mass in kg)
BMR vs. TDEE: What Is the Difference?
Many people confuse BMR (Basal Metabolic Rate) with TDEE (Total Daily Energy Expenditure), yet they represent two distinct numbers:
- BMR (Resting Baseline): The energy your body burns in a fasted, motionless state just to stay alive.
- TDEE (Total Daily Burn): Your complete 24-hour calorie expenditure. TDEE equals your BMR plus Non-Exercise Activity Thermogenesis (NEAT) (walking, standing, chores), Exercise Activity Thermogenesis (EAT) (workouts and sports), and the Thermic Effect of Food (TEF) (calories used to digest macronutrients).
In short, BMR is your metabolic foundation, while TDEE is your real-world daily maintenance calorie number.
How to Use the BMR Calculator
- Select Your Preferred Units: Choose between US Units (feet, inches, pounds) or Metric Units (centimeters, kilograms).
- Enter Age and Gender: Input your current age (15 to 80 years) and select Male or Female.
- Enter Height and Weight: Provide your accurate standing height and morning body weight.
- Choose a Calculation Formula: Keep the default Mifflin-St Jeor for general use, or switch to Katch-McArdle if you know your body fat percentage.
- Review BMR & Daily Calorie Needs: Click Calculate BMR to view your baseline metabolic rate alongside your estimated daily calorie requirements across five activity levels. Toggle between Calories and Kilojoules anytime.
Factors That Affect Your BMR
Two individuals of the exact same weight can have noticeably different Basal Metabolic Rates. Key physiological and environmental variables include:
- Body Composition & Muscle Mass: Skeletal muscle tissue burns significantly more energy at rest than adipose (fat) tissue. Higher lean mass directly elevates BMR.
- Body Size & Surface Area: Taller and heavier individuals have larger internal organs, greater blood volume, and more surface area to thermoregulate, increasing baseline energy requirements.
- Age: As adults age, gradual loss of lean muscle mass (sarcopenia) and slower cellular turnover cause BMR to decrease by roughly 1% to 2% per decade after age 20, with a steeper drop after age 60.
- Biological Sex: On average, men carry a higher ratio of skeletal muscle to fat mass than women of the same body weight, resulting in a 5% to 10% higher BMR.
- Genetics & Hormones: Thyroid hormones (T3 and T4), sympathetic nervous system tone, and inherited mitochondrial efficiency can raise or lower resting metabolic output.
- Environmental Temperature: Exposure to very cold or very hot climates forces the body to expend additional energy maintaining a stable core temperature of 98.6°F (37°C).
Is an Online BMR Calculator Accurate?
Online BMR calculators provide evidence-based statistical estimates, typically coming within 5% to 10% of laboratory values for most healthy adults. However, no mathematical formula can account for individual thyroid function, organ size variations, or adaptive thermogenesis from prior dieting.
For an exact clinical measurement, healthcare providers use indirect calorimetry—a laboratory test that measures oxygen consumption and carbon dioxide production through a breathing mask while you rest. Treat calculator outputs as a practical starting point rather than a medical diagnosis.
BMR and Weight Management
Understanding your BMR and TDEE empowers you to set realistic nutrition targets without guesswork:
- Weight Maintenance: Aim to consume approximately the number of calories listed next to your current activity level in the Daily Calorie Needs table.
- Sustainable Fat Loss: Create a moderate energy deficit of 300 to 500 calories below your estimated TDEE, prioritize dietary protein, and incorporate resistance exercise to preserve muscle mass. Avoid chronically eating below your baseline BMR without clinical supervision.
- Muscle Gain: Consume a controlled surplus of 200 to 350 calories above your TDEE paired with progressive strength training.