BMR Calculator
This BMR calculator estimates your Basal Metabolic Rate — the number of calories your body burns at rest to maintain basic functions like breathing, circulation, and cell production. Enter your age, gender, height, and weight to calculate your BMR using scientifically validated formulas.
Basal Metabolic Rate Calculator
Enter your details to calculate how many calories your body burns at rest and at various activity levels.
Frequently Asked Questions
What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, cell production, and nutrient processing while at complete rest. It represents the minimum energy expenditure needed to keep your body functioning and typically accounts for 60-75% of your total daily calorie burn.
How is BMR calculated?
BMR is calculated using predictive equations that factor in your age, gender, height, and weight. The two most widely used formulas are the Mifflin-St Jeor equation and the Harris-Benedict equation. These formulas were developed through clinical studies measuring oxygen consumption and carbon dioxide production to determine resting energy expenditure in diverse populations.
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation is considered the most accurate BMR formula for most people. For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5. For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161. Published in 1990, it has been validated as more accurate than the older Harris-Benedict equation.
What is the difference between BMR and TDEE?
BMR measures only the calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) includes all calories burned throughout the day including physical activity, exercise, and the thermic effect of food. TDEE is calculated by multiplying BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active). TDEE is the more practical number for diet planning.
Does BMR change with age?
Yes, BMR decreases with age, typically declining by about 1-2% per decade after age 20. This happens primarily due to the gradual loss of lean muscle mass (sarcopenia) and hormonal changes. This is one reason why many people find it harder to maintain their weight as they get older, even without changes in diet or activity level.
How can I increase my BMR?
The most effective way to increase BMR is to build lean muscle mass through resistance training, since muscle tissue burns more calories at rest than fat tissue. Other strategies include staying well-hydrated, getting adequate sleep, eating enough protein, and avoiding extreme calorie restriction which can lower your metabolic rate. High-intensity interval training (HIIT) can also temporarily boost metabolism.
What factors affect BMR?
Key factors affecting BMR include body composition (muscle-to-fat ratio), age, gender, height, weight, genetics, hormonal levels (especially thyroid hormones), and body temperature. Men generally have a higher BMR than women due to greater muscle mass. Environmental temperature, stress levels, certain medications, and overall health status can also influence your basal metabolic rate.
How to Calculate Your Basal Metabolic Rate (BMR)
What is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform its most basic life-sustaining functions, such as breathing, circulation, cell production, and nutrient processing. BMR represents the minimum amount of energy your body requires to function while at complete rest.
Your BMR typically accounts for 60–75% of your total daily energy expenditure. Understanding your BMR is essential for creating effective nutrition plans, whether your goal is weight loss, weight gain, or weight maintenance.
How to Use This Calculator
- Select your unit system: Imperial (feet, inches, pounds) or Metric (centimeters, kilograms).
- Enter your age in years.
- Select your gender (Male or Female).
- Enter your height and weight using the appropriate fields.
- Click "Calculate BMR" to see your results using both the Mifflin-St Jeor and Harris-Benedict formulas.
- Review the daily calorie needs table to find your estimated intake at your activity level.
BMR Formulas
Mifflin-St Jeor Equation (Recommended)
Developed in 1990, this is considered the most accurate formula for estimating BMR and is recommended by the Academy of Nutrition and Dietetics.
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Harris-Benedict Equation (Original)
Originally published in 1919 and revised in 1984, this is one of the earliest and most widely cited BMR equations.
Male: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age
Female: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age
For imperial inputs, the calculator automatically converts weight from pounds to kilograms (lbs × 0.453592) and height from feet/inches to centimeters ((ft × 12 + in) × 2.54) before applying the formulas.
Examples
Example 1: Male, Metric
A 30-year-old male, 180 cm tall, weighing 80 kg:
Mifflin-St Jeor: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1125 − 150 + 5 = 1,780 cal/day
Harris-Benedict: 88.362 + 13.397 × 80 + 4.799 × 180 − 5.677 × 30 = 88 + 1072 + 864 − 170 = 1,854 cal/day
Example 2: Female, Imperial
A 25-year-old female, 5'6" (167.6 cm), weighing 140 lbs (63.5 kg):
Mifflin-St Jeor: 10 × 63.5 + 6.25 × 167.6 − 5 × 25 − 161 = 635 + 1048 − 125 − 161 = 1,397 cal/day
Harris-Benedict: 447.593 + 9.247 × 63.5 + 3.098 × 167.6 − 4.330 × 25 = 448 + 587 + 519 − 108 = 1,446 cal/day
Activity Level Multipliers
To estimate your Total Daily Energy Expenditure (TDEE), multiply your BMR by the appropriate activity factor:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise | ×1.2 |
| Lightly active | Light exercise 1–3 days/week | ×1.375 |
| Moderately active | Moderate exercise 3–5 days/week | ×1.55 |
| Very active | Hard exercise 6–7 days/week | ×1.725 |
| Extra active | Very hard exercise or physical job | ×1.9 |
Use Cases
- Weight Loss: Understanding your BMR helps you create a calorie deficit by eating fewer calories than your TDEE.
- Weight Gain: Calculate how many additional calories you need above your TDEE to support muscle growth.
- Meal Planning: Use your TDEE to plan daily meals and macronutrient distribution.
- Fitness Programming: Trainers and coaches use BMR to design nutrition plans tailored to their clients' goals.
- Medical Assessment: Healthcare providers may use BMR to evaluate metabolic health and plan treatment strategies.
Tips and Considerations
Keep these important factors in mind when interpreting your BMR results:
- BMR calculations provide estimates. Individual metabolic rates can vary by 10–15% from calculated values.
- The Mifflin-St Jeor equation is generally considered more accurate for modern populations than the Harris-Benedict equation.
- BMR naturally decreases with age and with loss of lean body mass.
- Factors like genetics, hormones, body composition, and environmental temperature all influence actual metabolic rate.
- Never consume fewer calories than your BMR without medical supervision, as this can slow your metabolism and lead to nutrient deficiencies.
- For the most accurate measurement of metabolic rate, consider indirect calorimetry testing performed by a healthcare professional.
These formulas are designed for adults aged 18 and older. For children and adolescents, different equations such as the Schofield equation are more appropriate. Always consult a healthcare provider for personalized dietary advice.