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BMR Calculator (Basal Metabolic Rate)

Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). Get personalized calorie targets for weight loss, maintenance, and weight gain.

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BMR Calculator. Basal metabolic rate and daily calorie needs.
A BMR calculator estimates the calories your body burns at rest using formulas like Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle. It multiplies your BMR by an activity factor to determine your Total Daily Energy Expenditure (TDEE) and personalized calorie targets for weight loss, maintenance, or gain.

What Is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain essential life functions such as breathing, circulation, cell production, and temperature regulation. BMR accounts for roughly 60-70% of your total daily calorie expenditure, making it the single largest component of the calories you burn each day.
BMR is measured under strict laboratory conditions: after 12 hours of fasting, 8 hours of sleep, and in a temperature-neutral environment. In practical terms, your BMR represents the minimum energy your body needs just to stay alive without any physical movement or digestion. For the average American man, BMR is approximately 1,600-1,800 calories per day; for women, it ranges from 1,300-1,500 calories per day.
Understanding your BMR is essential for anyone managing their weight, planning a nutrition program, or optimizing athletic performance. When you know your BMR, you can calculate your Total Daily Energy Expenditure (TDEE) by factoring in physical activity, and from there determine the exact calorie intake needed to lose fat, maintain weight, or build muscle.

How to Calculate Your BMR Step by Step

To calculate your BMR, you need four pieces of information: your weight, height, age, and biological sex. The most widely recommended equation is the Mifflin-St Jeor formula, which studies have shown to be accurate within 10% of measured values for most people.
Here is the step-by-step process:
1. Convert your weight to kilograms. Divide your weight in pounds by 2.205 (for example, 180 lbs = 81.6 kg).
2. Convert your height to centimeters. Multiply your height in inches by 2.54 (for example, 5'10" = 70 inches = 177.8 cm).
3. Apply the Mifflin-St Jeor formula. For men: (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5. For women: (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161.
4. The result is your BMR in calories per day.
5. To find your TDEE, multiply your BMR by an activity factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, or 1.9 for extremely active.
For example, a 30-year-old man weighing 180 lbs (81.6 kg) and standing 5'10" (177.8 cm) tall has a BMR of approximately 1,829 calories per day. If he exercises 3-5 days per week (moderately active), his TDEE would be about 2,835 calories per day.

BMR Formulas: Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle

BMR=(10×W)+(6.25×H)−(5×A)+SBMR = (10 \times W) + (6.25 \times H) - (5 \times A) + S
  • WW = Body weight in kilograms
  • HH = Height in centimeters
  • AA = Age in years
  • SS = Sex constant: +5 for men, -161 for women
The formula above is the Mifflin-St Jeor equation, developed in 1990 and considered the gold standard for BMR estimation by the American Dietetic Association. Studies show it predicts measured BMR within 10% for most individuals, compared to up to 36% error rates with older equations in certain populations.
The Revised Harris-Benedict equation (1984) is an older alternative:
BMRmale=88.362+(13.397×W)+(4.799×H)−(5.677×A)BMR_{male} = 88.362 + (13.397 \times W) + (4.799 \times H) - (5.677 \times A)
BMRfemale=447.593+(9.247×W)+(3.098×H)−(4.330×A)BMR_{female} = 447.593 + (9.247 \times W) + (3.098 \times H) - (4.330 \times A)
The Katch-McArdle formula uses lean body mass instead of total weight, making it potentially more accurate for athletes and lean individuals who know their body fat percentage:
BMR=370+(21.6×LBM)BMR = 370 + (21.6 \times LBM)
where LBM (lean body mass in kg) = weight in kg x (1 - body fat percentage / 100).
For TDEE, multiply your BMR by an activity multiplier:
TDEE=BMR×ActivityFactorTDEE = BMR \times ActivityFactor
Activity factors range from 1.2 (sedentary, desk job with no exercise) to 1.9 (extremely active, hard physical labor or two-a-day training sessions).

BMR and TDEE Calculation Examples

Example: 30-Year-Old Man Trying to Lose Weight

John is a 30-year-old man who weighs 200 lbs (90.7 kg) and stands 5'11" (180.3 cm). He works a desk job and exercises 3 days per week (moderately active).
Using the Mifflin-St Jeor formula: BMR = (10 x 90.7) + (6.25 x 180.3) - (5 x 30) + 5 = 907 + 1,127 - 150 + 5 = 1,889 calories/day.
His TDEE at moderate activity (x 1.55) = 2,928 calories/day.
To lose 1 pound per week, John needs a 500-calorie daily deficit, so his target intake would be approximately 2,428 calories per day. To lose 0.5 lbs per week (a more conservative approach), he would aim for about 2,678 calories per day.

Example: 25-Year-Old Woman Building Muscle

Sarah is a 25-year-old woman who weighs 140 lbs (63.5 kg) and is 5'6" (167.6 cm) tall. She does strength training 5 days per week (very active).
Using the Mifflin-St Jeor formula: BMR = (10 x 63.5) + (6.25 x 167.6) - (5 x 25) - 161 = 635 + 1,048 - 125 - 161 = 1,397 calories/day.
Her TDEE at very active (x 1.725) = 2,410 calories/day.
To gain lean muscle at a controlled rate of about 0.5 lbs per week, Sarah should eat roughly 250 calories above her TDEE, targeting approximately 2,660 calories per day with a focus on adequate protein intake (around 0.7-1.0 g per pound of body weight).

Example: Comparing All Three Formulas

Mike is a 35-year-old man who weighs 175 lbs (79.4 kg), is 5'9" (175.3 cm) tall, and has 18% body fat.
Mifflin-St Jeor: BMR = (10 x 79.4) + (6.25 x 175.3) - (5 x 35) + 5 = 794 + 1,096 - 175 + 5 = 1,720 cal/day.
Revised Harris-Benedict: BMR = 88.362 + (13.397 x 79.4) + (4.799 x 175.3) - (5.677 x 35) = 88 + 1,064 + 841 - 199 = 1,794 cal/day.
Katch-McArdle: Lean body mass = 79.4 x (1 - 0.18) = 65.1 kg. BMR = 370 + (21.6 x 65.1) = 1,776 cal/day.
All three formulas produce results within 74 calories of each other (1,720-1,794), confirming that for most people the choice of formula matters less than accurately tracking your actual calorie intake and adjusting based on real-world results.

Tips to Optimize Your Metabolism and Use BMR Effectively

  • Build and maintain muscle mass. Muscle tissue burns approximately 6 calories per pound per day at rest, compared to just 2 calories per pound for fat. Strength training 2-4 times per week is the most effective way to raise your BMR over time.
  • Eat enough protein. Protein has the highest thermic effect of food at 15-30%, meaning your body uses 15-30% of protein calories just for digestion. Aim for 0.7-1.0 grams of protein per pound of body weight daily to support muscle and metabolism.
  • Do not crash diet. Severe calorie restriction (eating far below your BMR) triggers metabolic adaptation, causing your body to lower its BMR by up to 20%. Stick to a moderate deficit of 250-500 calories below your TDEE for sustainable fat loss.
  • Recalculate your BMR every 10-15 pounds of weight change. As your body weight decreases, your BMR drops too. A person who has lost 20 lbs will burn roughly 100-200 fewer calories per day, which explains why weight loss plateaus occur.
  • Prioritize quality sleep. Research shows that chronic sleep deprivation (fewer than 7 hours per night) can reduce BMR by 2-8% and increase hunger hormones. Aim for 7-9 hours of sleep nightly to keep your metabolism functioning optimally.
  • Stay hydrated throughout the day. Studies indicate that drinking 500 ml (about 17 oz) of water can temporarily boost metabolic rate by 24-30% for about an hour. Drinking cold water may have a slightly larger effect as your body expends energy warming it.

Frequently Asked Questions About BMR

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain vital functions. TDEE (Total Daily Energy Expenditure) is your BMR plus all additional calories burned through daily activities, exercise, and digesting food. TDEE is always higher than BMR. For example, if your BMR is 1,600 calories and you are moderately active, your TDEE would be approximately 2,480 calories (1,600 x 1.55). You should base your calorie goals on TDEE, not BMR, because eating below your BMR for extended periods can be harmful.

Which BMR formula is the most accurate?

The Mifflin-St Jeor equation is considered the most accurate for the general population and is recommended by the American Dietetic Association. Studies have shown it predicts measured BMR within 10% for most individuals. The Harris-Benedict equation tends to overestimate by about 5%. The Katch-McArdle formula can be more accurate for lean, athletic individuals who know their body fat percentage, but its accuracy decreases significantly in people with higher body fat levels. For most people, the Mifflin-St Jeor formula is the best starting point.

What is a normal BMR for my age and sex?

Average BMR varies significantly based on age, sex, height, and weight. As a general reference: men aged 20-30 typically have a BMR of 1,600-1,900 calories per day, while women in the same age range average 1,300-1,500 calories per day. BMR gradually decreases with age, dropping roughly 1-2% per decade after age 20, with a more pronounced decline after age 60 (approximately 0.7% per year). However, individual variation is large, so it is more useful to calculate your personal BMR using your specific measurements than to rely on averages.

How many calories should I eat to lose weight based on my BMR?

To lose weight, you should eat below your TDEE (not your BMR). First, calculate your TDEE by multiplying your BMR by your activity level. Then subtract 250-500 calories from your TDEE for a safe, sustainable deficit. A 500-calorie daily deficit produces approximately 1 pound of fat loss per week. A 250-calorie deficit produces about 0.5 lbs per week. Never eat below your BMR for extended periods, as this can trigger metabolic adaptation, muscle loss, and nutritional deficiencies.

Can I increase my BMR?

Yes, you can increase your BMR primarily by building lean muscle mass through strength training. Each pound of muscle burns about 6 calories per day at rest, compared to 2 calories per pound of fat. Other factors that can modestly boost BMR include eating adequate protein (which increases the thermic effect of food by 15-30%), staying well-hydrated, getting 7-9 hours of quality sleep, and avoiding prolonged severe calorie restriction. While genetics play a significant role in your baseline metabolic rate, these lifestyle factors can meaningfully shift your BMR over time.

Why does my BMR decrease as I lose weight?

Your BMR decreases during weight loss for two reasons. First, a smaller body simply requires less energy to maintain, so as you lose mass, your calorie needs naturally drop. Second, your body undergoes metabolic adaptation (sometimes called "adaptive thermogenesis"), where it becomes more efficient at using energy to conserve fuel. This adaptation can reduce BMR by an additional 5-15% beyond what weight loss alone would predict. This is why weight loss often slows or plateaus over time and why recalculating your BMR every 10-15 lbs lost is important for staying on track.

What is the difference between BMR and RMR?

BMR (Basal Metabolic Rate) and RMR (Resting Metabolic Rate) are closely related but measured under slightly different conditions. BMR requires 12 hours of fasting, 8 hours of sleep, and a controlled laboratory environment. RMR is measured under less strict conditions (usually just a few hours of fasting and a short rest period), making it more practical to test clinically. RMR is typically 10-20% higher than BMR because it includes some residual energy from recent digestion and activity. For practical purposes, the two values are often used interchangeably in calorie planning.

Should I eat below my BMR to lose weight faster?

No, eating below your BMR is not recommended and can be counterproductive. When you consistently consume fewer calories than your BMR, your body enters a survival mode that slows metabolism, breaks down muscle tissue for energy, disrupts hormones (including thyroid and leptin), and increases hunger and cravings. This often leads to the "yo-yo" effect where weight is regained rapidly after the diet ends. Instead, calculate your TDEE and create a moderate deficit of 250-500 calories below that number. This approach preserves muscle mass, maintains metabolic rate, and produces sustainable, long-term fat loss.

Key Terms

Basal Metabolic Rate (BMR)

The number of calories your body burns at complete rest to sustain basic life functions such as breathing, circulation, and cell repair. Measured after 12 hours of fasting in a controlled environment.

Total Daily Energy Expenditure (TDEE)

The total number of calories you burn in a day, including BMR, physical activity, and the thermic effect of food. Calculated by multiplying BMR by an activity factor (1.2 to 1.9).

Mifflin-St Jeor Equation

A BMR estimation formula developed in 1990 that uses weight, height, age, and sex. Considered the most accurate predictive equation for the general population by the American Dietetic Association.

Thermic Effect of Food (TEF)

The energy your body uses to digest, absorb, and process nutrients. TEF accounts for about 10% of total calorie intake, with protein requiring the most energy (15-30% of its calories).

Lean Body Mass (LBM)

Your total body weight minus your fat mass. LBM includes muscle, bones, organs, and water. Used in the Katch-McArdle BMR formula for more accurate estimates in lean individuals.

Metabolic Adaptation

The process by which your body reduces its metabolic rate in response to prolonged calorie restriction. Also called adaptive thermogenesis, it can lower BMR by 5-15% beyond what weight loss alone would predict.

Calorie Deficit

Consuming fewer calories than your TDEE, forcing your body to use stored energy (primarily fat) for fuel. A deficit of 500 calories per day produces approximately 1 pound of fat loss per week.