BMR Calculator

What is BMR (Basal Metabolic Rate)? Definition and Importance

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions such as breathing, blood circulation, cell production, brain and nerve function, and maintaining body temperature. It represents approximately 60-75% of your total daily calorie expenditure for most people.

BMR is different from your resting metabolic rate (RMR), though the terms are often used interchangeably. RMR is typically measured in a lab after a period of rest, while BMR requires more strict conditions (fasting, complete rest, controlled temperature). For practical purposes, BMR and RMR are very similar, and BMR calculators provide a good estimate of your metabolic rate.

Understanding your BMR is crucial because it forms the foundation for calculating your daily calorie needs. Whether you want to lose weight, gain muscle, or maintain your current weight, knowing your BMR helps you create an appropriate nutrition plan. A calorie deficit (eating less than your TDEE) leads to weight loss, while a calorie surplus (eating more than your TDEE) leads to weight gain.

Several factors influence your BMR, including age (BMR decreases with age), gender (men typically have higher BMR due to more muscle mass), body composition (muscle burns more calories than fat), height and weight (larger bodies require more energy), and genetics. While you can't change your genetics, you can increase your BMR by building muscle through strength training.

BMR Formulas: Understanding Different Calculation Methods

Our BMR calculator uses five different formulas, each with its own strengths and applications. Understanding the differences helps you choose which result to use for your specific situation.

Mifflin-St Jeor Equation (1990) – Recommended

The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population and is the current gold standard. It was developed in 1990 and is more accurate than older formulas because it was based on a larger, more diverse population sample. This formula is recommended by the Academy of Nutrition and Dietetics and is our default calculation method.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(years) + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(years) - 161

Harris-Benedict Equation (Revised, 1984)

The revised Harris-Benedict equation is an updated version of the original 1919 formula. It's still widely used and provides accurate results for most people, though it tends to slightly overestimate BMR compared to Mifflin-St Jeor.

Harris-Benedict Equation (Original, 1919)

The original Harris-Benedict equation was one of the first BMR formulas developed. While it's less accurate than modern formulas (it was based on a smaller, less diverse sample), it's included for historical reference and comparison.

Katch-McArdle Formula (1996)

The Katch-McArdle formula is unique because it uses lean body mass (LBM) instead of total body weight. This makes it more accurate for athletes and individuals with known body fat percentage, as it accounts for the fact that muscle tissue burns more calories than fat tissue. Formula: BMR = 370 + (21.6 × lean body mass in kg).

Cunningham Formula (1980)

Similar to Katch-McArdle, the Cunningham formula also uses lean body mass and is particularly accurate for athletes and bodybuilders. Formula: BMR = 500 + (22 × lean body mass in kg).

How to Use BMR for Weight Loss

To lose weight effectively and sustainably, you need to create a calorie deficit. Here's how to use your BMR and TDEE for weight loss:

1. Calculate your TDEE: Use the calculator above to determine your Total Daily Energy Expenditure based on your activity level.
2. Create a moderate deficit: Subtract 250-500 calories from your TDEE. This creates a deficit of 1,750-3,500 calories per week, leading to approximately 0.5-1 pound of weight loss per week.
3. Never go below your BMR: Your daily calorie intake should never fall below your BMR, as this can slow down your metabolism and lead to muscle loss.
4. Prioritize protein: When in a calorie deficit, aim for 0.8-1 gram of protein per pound of body weight to preserve muscle mass.
5. Combine with exercise: Strength training helps preserve muscle mass during weight loss, while cardio increases your calorie burn.
6. Reassess regularly: As you lose weight, your BMR decreases. Recalculate your BMR and TDEE every 10-15 pounds of weight loss.

Example: If your TDEE is 2,000 calories, aim to consume 1,500-1,750 calories per day for steady weight loss. This creates a sustainable deficit without feeling overly restricted.

How to Use BMR for Muscle Gain

Building muscle requires a calorie surplus combined with progressive strength training. Here's how to use your BMR and TDEE for muscle gain:

1. Calculate your TDEE: Determine your Total Daily Energy Expenditure, accounting for your training schedule.
2. Create a moderate surplus: Add 250-500 calories to your TDEE. This provides the extra energy needed for muscle protein synthesis without excessive fat gain.
3. Prioritize protein: Aim for 1-1.2 grams of protein per pound of body weight to support muscle growth and recovery.
4. Strength train consistently: Engage in progressive resistance training 3-5 times per week, focusing on compound movements.
5. Monitor progress: Track your weight, body measurements, and strength gains. Adjust calories if you're gaining too much fat or not gaining weight.

Example: If your TDEE is 2,500 calories, aim to consume 2,750-3,000 calories per day while following a structured strength training program.

Factors That Affect Your BMR

Several factors influence your Basal Metabolic Rate. Understanding these can help you optimize your metabolism:

• Age: BMR decreases by approximately 1-2% per decade after age 20 due to loss of muscle mass and hormonal changes.
• Gender: Men typically have 5-10% higher BMR than women due to greater muscle mass and lower body fat percentage.
• Body Composition: Muscle tissue is metabolically active and burns more calories at rest than fat tissue. The more muscle you have, the higher your BMR.
• Body Size: Larger individuals (taller or heavier) have higher BMR because they have more tissue to maintain.
• Genetics: Some people naturally have faster or slower metabolisms due to genetic factors.
• Hormones: Thyroid hormones, growth hormone, and sex hormones (testosterone, estrogen) influence metabolic rate.
• Diet: Severe calorie restriction can lower BMR (metabolic adaptation), while adequate protein and regular meals can help maintain it.
• Sleep: Poor sleep quality and insufficient sleep can lower BMR and disrupt hormones that regulate metabolism.
• Stress: Chronic stress and elevated cortisol levels can affect metabolism and body composition.

Tips to Increase Your BMR Naturally

While you can't change your age, gender, or genetics, you can take steps to increase your BMR and improve your metabolism:

• Build Muscle: Strength training 2-3 times per week increases muscle mass, which raises your BMR. Each pound of muscle burns approximately 6-7 calories per day at rest.
• Eat Enough Protein: Protein has a higher thermic effect of food (TEF) than carbs or fats, meaning your body burns more calories digesting it. Aim for 0.8-1 gram per pound of body weight.
• Stay Hydrated: Drinking water can temporarily boost metabolism. Cold water may be especially effective as your body burns calories warming it.
• Get Quality Sleep: Aim for 7-9 hours of quality sleep per night. Poor sleep disrupts hormones that regulate metabolism and appetite.
• Manage Stress: Chronic stress elevates cortisol, which can slow metabolism and promote fat storage, especially around the abdomen.
• Avoid Severe Calorie Restriction: Eating too few calories can cause your body to lower BMR to conserve energy. Aim for a moderate deficit of 250-500 calories.
• Stay Active: Regular physical activity, including both cardio and strength training, helps maintain muscle mass and metabolic rate.