BMR Calculator

Basal Metabolic Rate (BMR) is the amount of energy your body needs while at complete rest to maintain vital functions such as breathing, circulation, cell production, nutrient processing, and brain function. It represents the minimum number of calories required to keep your body functioning at rest.

BMR typically accounts for 60-75% of your total daily energy expenditure, making it the largest component of your calorie needs. Understanding your BMR is essential for effective weight management, nutritional planning, and setting realistic fitness goals.

BMR is measured under very specific conditions: complete physical and mental rest, in a fasting state (12-14 hours after eating), in a neutral temperature environment. In practical settings, Resting Metabolic Rate (RMR) is often measured instead, which is slightly higher than BMR but follows similar principles.

Our calculator offers three different formulas to estimate your BMR:

1. Harris-Benedict Equation: A widely used formula that considers your gender, age, weight, and height.
2. Mifflin-St Jeor Equation: A more recent formula (1990) that many nutritionists consider more accurate for the average person.
3. Katch-McArdle Formula: A formula that uses lean body mass instead of total weight, potentially providing more accurate results for athletic individuals.

To calculate your BMR:

1. Select your gender
2. Enter your age in years
3. Enter your weight (in kg or lb)
4. Enter your height (in cm or inches)
5. If you want to use the Katch-McArdle formula, check the box and enter your body fat percentage
6. Click the "Calculate" button

The calculator will display your BMR according to each selected formula, allowing you to compare the results.

Harris-Benedict Equation (Revised 1984):

For men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)

For women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)

Mifflin-St Jeor Equation (1990):

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

Katch-McArdle Formula:

BMR = 370 + (21.6 × Lean Body Mass in kg)

Where Lean Body Mass (LBM) = Total Weight × (1 - (Body Fat Percentage / 100))

Each BMR formula has its strengths and potential limitations:

• Harris-Benedict: One of the oldest and most widely used equations. The revised version (1984) improved accuracy over the original 1919 formula. It works well for most people but may overestimate BMR in some cases.
• Mifflin-St Jeor: Developed in 1990, this formula is considered by many nutritionists to be more accurate than Harris-Benedict for the general population. Research suggests it's the most accurate for non-obese individuals.
• Katch-McArdle: By using lean body mass instead of total weight, this formula can provide more accurate results for athletic individuals or those with higher muscle mass. However, it requires knowing your body fat percentage, which can be difficult to measure accurately.

The differences between these formulas are typically within 10% for most people. If you're unsure which to use, Mifflin-St Jeor is generally recommended for the average person, while Katch-McArdle may be better for athletic individuals if you have an accurate body fat measurement.

Understanding your BMR has several practical applications:

• Weight management: Knowing your BMR helps establish a baseline for calorie needs, essential for weight loss, maintenance, or gain.
• Nutritional planning: BMR forms the foundation for calculating your total daily energy expenditure (TDEE) and creating personalized meal plans.
• Fitness goal setting: Understanding your metabolic rate helps set realistic fitness and body composition goals.
• Metabolic health assessment: BMR can provide insights into your metabolic health and efficiency.

To calculate your total daily energy expenditure (TDEE), multiply your BMR by an activity factor:

• Sedentary (little or no exercise): BMR × 1.2
• Lightly active (light exercise 1-3 days/week): BMR × 1.375
• Moderately active (moderate exercise 3-5 days/week): BMR × 1.55
• Very active (hard exercise 6-7 days/week): BMR × 1.725
• Extremely active (very hard exercise, physical job or training twice a day): BMR × 1.9

Several factors influence your basal metabolic rate:

• Body composition: Muscle tissue requires more energy to maintain than fat tissue. People with higher muscle mass typically have higher BMRs.
• Age: BMR typically decreases with age, partly due to the loss of muscle mass and hormonal changes.
• Gender: Men generally have higher BMRs than women due to greater muscle mass and lower body fat percentages.
• Genetics: Some people naturally have faster or slower metabolisms due to genetic factors.
• Hormonal factors: Thyroid hormones, growth hormone, and other hormones significantly impact metabolic rate.
• Body size and weight: Larger bodies generally require more energy to maintain basic functions.
• Environmental temperature: Extreme temperatures can increase BMR as the body works to maintain core temperature.
• Health conditions: Certain medical conditions and medications can affect BMR.
• Nutritional status: Severe calorie restriction can lower BMR as the body adapts to conserve energy.