BMR Calculator
A Basal Metabolic Rate (BMR) calculator estimates the number of calories your body burns daily at rest. Combine this with our calorie calculator to support your weight loss goals.
Recommended calories intake
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Basal Metabolic Rate (BMR) is a measure of baseline energy expenditure or the number of calories your body burns to perform basic life functions when you are at rest. BMR calculation is the first crucial step towards managing your weight and overall health. You can manage your weight with the help of TDEE (total daily energy expenditure), and BMR is the major component of TDEE.
You might have seen generic caloric recommendations everywhere on the internet describing how many calories you should consume and how many you should burn. The question is, are these recommendations the same for everyone? Do they help manage weight? A straightforward answer is, No! Each person has a different metabolism, and their caloric needs are also different. Calculating BMR is the first step in measuring how many calories you need per day.
This blog provides a comprehensive guide on how to accurately calculate your BMR and understand its influencing factors, explains how it differs from TDEE and mentions its role in achieving your fitness and health goals.
In simple terms, BMR is the minimum number of calories your body burns at rest to maintain essential life functions such as breathing, circulation, digestion, organ function, nerve function, and cell production. In other words, it is the number of calories your body needs to perform basic life-sustaining functions.
BMR represents the energy your body needs just to exist without any activity. For example, if you are sitting on a couch without doing anything, your body is still working. It is still burning calories to perform basic life functions.
Basal metabolic rate (BMR) and resting energy expenditure (REE) or resting metabolic rate (RMR) are used interchangeably. Both are slightly different. BMR is an estimate of how many calories are required for your body to perform basic functions, while REE is the actual number of calories your body burns when it is at rest. BMR and RMR vary by approximately 10%.
BMR is a foundational metric for understanding your overall energy needs.
BMR helps manage weight. Whether you want to lose or gain weight, it will help you understand how many calories your body needs. Basal metabolic rate also helps you avoid metabolic slowdown when managing weight.
When you are at rest, your body is still working and burning calories to perform different physiological functions such as maintaining body temperature, cellular activities, brain functions, blood circulation, digestion, and respiration. The basal metabolic rate reflects calorie expenditure for performing these basic functions.
However, BMR does not take account of calorie expenditure when performing any physical activity such as walking, running, exercise or any other activity.
BMR calculation formulas are different for men and women. You will need to plug your age in years, weight (in kilograms and pounds), and height (in centimeters and inches) into each of the primary formulas (Mifflin-St Jeor and revised Harris-Benedict) to calculate BMR manually.
You can use reputable online calculators such as the NiceRx BMR Calculator to measure your basal metabolic rate. However, do not blindly follow any calculator. First, understand which formula the calculator uses and how accurate the formula is.
The Harris-Benedict formula uses your current weight, height, age, and gender. The original Harris-Benedict equation was developed in 1919 and has been widely used to estimate an individual’s Basal Metabolic Rate (BMR). However, as populations changed, it was found that the original equation tended to overestimate BMR, especially in overweight individuals.
BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years)
BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years)
The Revised Harris-Benedict equation, developed in 1984, was intended to correct the overestimation of BMR found in the original formula.
BMR = 655 + (9.6 x body weight) + (1.8 x height) – (4.7 x age)
66 + (13.7 x body weight) + (5 x height) – (6.8 x age)
The American Council on Exercise (ACE) states that the Mifflin-St Jeor formula is more accurate than the Harris-Benedict equation as it accounts for lean body mass better.
Katch McArdle formula is better for sportsmen, athletes, and those who know their lean body mass or body fat percentage.
BMR = 370 + (21.6 × Lean Body Mass [kg])
You can calculate your Lean Body Mass (LBM) using the Boer formula, as shown below:
Lean Body Mass = 0.407 x body weight [kg] + 0.267x height [cm] – 19.2
Lean Body Mass = 0.252 x body weight [kg] + 0.473 x height [cm] – 48.3
Let’s calculate BMR using the Mifflin-St Jeor formula:
For example, you are a 40-year-old female, with a 5’4” height, 70 kg (154 lbs) weight, and you are slightly active.
BMR = 9.99 x body weight in Kgs + 6.25 x height in cms – 4.92 x age in years – 161
Let’s insert values:
It means your body requires 1,357.5 calories for basic life functions when you are at rest and not doing any activity.
Now, you can also calculate your TDEE (total daily energy expenditure) with the help of the NiceRx TDEE calculator or manually (TDEE = BMR x Activity level).
The following factors influence basal metabolic rate:
As we age, BMR (Basal Metabolic Rate) decreases mainly due to a loss of skeletal muscle mass and an increase in body fat. Muscle burns the most energy, so the body’s energy expenditure drops when muscle mass declines. As muscles atrophy, older people tend to move less and become more sedentary, which also lowers energy needs. Additionally, reduced physical activity and increased abdominal fat further lower energy needs. Abdominal fat also disrupts glucose and lipid metabolism, which contributes to a decline in glucose tolerance.
Men and women have different basal metabolic rates as their body composition differs. Men have higher muscle mass and a higher proportion of muscle to fat. They have a higher BMR because muscles burn more calories, which leads to higher energy expenditure at rest. In comparison, women have lower muscle mass and a lower BMR.
There is a direct correlation between body weight, body mass index, and BMR. Heavier individuals have greater muscle mass, and they generally have a higher BMR to support a larger body mass. In contrast, people with less body weight have lower BMR due to small muscle mass and less energy expenditure.
Taller individuals usually have a slightly higher BMR than shorter ones due to a larger surface area and greater organ mass. The body needs additional calories to support the larger surface area and greater tissue volume. In contrast, shorter individuals typically have a smaller body size and less mass. Their bodies burn fewer calories at rest, and they have a lower BMR.
Your BMR depends on body composition. Suppose you have greater lean muscle tissue than fat tissue. In that case, you will metabolically be more active than individuals with the same weight but greater fat tissue because muscles burn more calories. On the other hand, fat tissues are less metabolically active and burn fewer calories. Individuals with higher fat mass have lower BMR.
Genetics plays a significant role in determining BMR (Basal Metabolic Rate). Some individuals have genetically higher or lower BMR based on several factors, such as hormone levels, muscle fiber type, and metabolic efficiency. For example, people with a family history of faster metabolism may have a higher BMR. Their bodies will burn more calories at rest. In contrast, people with a genetic tendency toward slower metabolism may have a lower BMR. Genetics can set the baseline for how efficiently the body burns energy.
Many endogenous hormones, such as DHEAS (dehydroepiandrosterone sulphate), thyroid hormone, and cortisol, impact BMR. Thyroid hormones (T3 and T4) directly influence BMR. Hyperthyroidism is a condition in which thyroid hormone is elevated. Individuals with hyperthyroidism have higher BMR. In contrast, hypothyroidism (low thyroid hormone levels) reduces basal metabolic rates.
Additionally, men have higher DHEAS levels that contribute to higher muscle mass and BMR. A research study shows that DHEAS has a positive association with BMR in obese individuals.
Individuals working at extreme temperatures (whether extremely hot or cold) can have a slightly increased BMR compared to others. Their bodies burn extra calories to maintain body temperature. In an extremely cold environment, the body activates mechanisms like shivering and increased fat oxidation to generate heat. These mechanisms increase energy expenditure at rest.
Dieting and calorie restriction for prolonged periods can decrease BMR. The body adapts to lower calorie intake and tries to conserve energy for bodily functions. Research studies reflect that calorie restriction can massively reduce the body’s energy expenditure.
TDEE (Total Daily Energy Expenditure) is the total number of calories you burn in a day (24 hours). These include BMR, the thermic effect of food (TEF), non-exercise activity thermogenesis (NEAT), and exercise activity thermogenesis (EAT). TDEE accounts for calories burned in the body’s own functions as well as during physical activities. In comparison, BMR is the amount of energy needed for basic life-sustaining functions. It does not reflect the number of calories burned during physical activity. It is a measure of energy expenditure at rest only.
Think of your body as a vehicle. When you switch it on, its engine starts consuming fuel even if you are not moving. So, BMR is similar to the fuel consumed when the vehicle is switched on but not moving. In comparison, TDEE is the same as total fuel consumption during motion when you speed up, take turns, stop, or accelerate your vehicle. While BMR represents the fuel your body uses at rest, TDEE tracks the energy burned through all activities, whether at rest or on the move.
BMR is just one component of TDEE. Your activity level plays a significant role in your total daily calorie needs. Individuals with higher activity levels have higher TDEE.
TDEE is calculated as: TDEE = BMR × physical activity
| Activity Level | Description | TDEE |
|---|---|---|
| Sedentary | Little to no physical activity. | BMR x 1.2 |
| Lightly active | Moderate exercise 1 to 3 times per week (for at least 20 minutes), or a busy lifestyle involving frequent walking. Examples include skating, jogging, cycling, jogging, or swimming. | BMR x 1.375 |
| Moderately active | Regular exercise 3 to 4 times per week (for 30 to 60 minutes). Examples include strength training | BMR x 1.55 |
| Active | Vigorous exercise for 60 minutes or more 5 to 7 days per week, or physically demanding jobs like construction, farming, or landscaping. | BMR x 1.725 |
| Very active | Highly intense activity, including multiple training sessions each day for athletes or very physically demanding work such as assembly line labor or coal shoveling. | BMR x 1.9 |
You can use BMR in the following ways to achieve your weight management goals:
Calculate your TDEE using your BMR and activity level multiplier. For weight loss, you need to consume fewer calories than your TDEE. It will create a calorie deficit. The body will use fats to overcome calorie deficit, and you will lose extra weight.
For sustainable weight loss, create a calorie deficit of 500-700 calories below TDEE. It may help you lose 1-1.5 pounds per week. Consuming 20% less calories than TDEE helps you lose weight aggressively while consuming 10% fewer calories than TDEE leads to sustainable weight loss.
Always stay within a safe range of calorie deficit. Otherwise, it can lead to nutritional deficiencies and metabolic damage.
To gain weight, you need to consume more calories than your TDEE. Add a moderate calorie surplus of 250-500 calories above TDEE. Adding 5-10% surplus calories to TDEE adds lean bulk to your body. If you consume 15% or more extra calories, it will add fat mass to your body.
Add protein-rich foods and healthy fats to your diet to increase muscle mass. Do not add junk foods, processed snacks, sugary drinks, and fatty foods to your diet. They may lead to obesity and body disfigurement associated with being overweight.
If you do not want to lose or gain weight and want to maintain your current weight, try to consume the same number of calories as your TDEE. When the body’s energy expenditure is equal to caloric intake, you do not gain or lose weight.
However, it is important to remember that TDEE can fluctuate based on several factors such as activity changes, changes in body weight, and use of certain medications such as weight loss medications, medications for thyroid problems and diabetes, and antipsychotics.
In case of these changes, recalculate your TDEE and make necessary adjustments to calorie intake.
Additionally, incorporate exercise and a balanced diet in your daily routine to maintain your weight. Keep in mind that TDEE is not a 100% accurate calculation of your caloric needs. It is just an estimate of your body’s energy expenditure in 24 hours. That is why you should focus on lifestyle modifications too.
Weight does not occur only due to low BMR. Other factors such as higher fat mass, a sedentary lifestyle, and an unhealthy diet contribute to weight gain.
BMR varies from person to person. It is influenced by several factors like age, gender, body composition, genetics, and activity level. For example, individuals with more muscle mass generally have a higher BMR than those with more body fat, despite having the same body weight.
BMR represents the energy your body uses at rest to maintain essential functions such as breathing, circulation, nerve functions, cellular processes, and temperature regulation. It does not include the calories burned from physical activity, which is accounted for by TDEE (Total Daily Energy Expenditure).
You can’t drastically change your BMR overnight. There is no magic food or supplement that can drastically increase it
A balanced diet and regular exercise can help optimize metabolism, but changes take time. If you want to increase your BMR, increase your body’s muscle mass.
BMR declines with age due to loss of muscle mass and less physical activity but it doesn’t decrease drastically in a short period. If you maintain an active lifestyle and incorporate strength training into your routine, it can slow down the natural decline in BMR as you age.
While the thermic effect of food (TEF) does contribute to energy expenditure, its percentage is relatively smaller compared to factors like muscle mass and activity level. Eating excessively doesn’t significantly increase your BMR and can lead to weight gain instead.
BMR can fluctuate over time depending on several factors such as changes in body composition, activity levels, use of certain medications, and comorbidities. For example, if you use weight loss medications, they slow down the process of digestion and suppress appetite. Decreased body weight can change your BMR.
Certain lab tests can provide a precise measurement of BMR, but estimates based on equations (like the Harris-Benedict or Mifflin-St Jeor formula) are also helpful.
BMR calculations are estimates of how many calories your body burns while at rest, but individual needs may vary. For example, if you have higher muscle mass, your body will burn more calories than an individual with higher fat mass, even if the body is the same. Always focus on your body needs, hunger cues, and energy levels, and monitor your progress continuously when adjusting calorie intake. Do not take any diet plan recommended for others with the same BMR or TDEE. Your body’s needs might be different from others.
Consult with a registered dietitian or nutritionist for personalized guidance on BMR, TDEE, and a balanced diet to achieve your weight management goals.
The following are a few tips to boost your BMR naturally:
Strict calorie restriction for a longer time or going into starvation mode does not work. Initially, the body increases BMR during fasting. After extreme calorie restriction, the body adopts a lower BMR to preserve energy.
Products such as detox teas or metabolism pills do not work. Although they are marketed as miracle pills to enhance BMR, they do not offer the same benefits.
Your BMR can change daily if you experience wide variations in energy intake, but these variations are very small and unlikely to be important.
BMR depends on several factors such as age, weight, height, body composition, genetics, dietary habits, and environmental temperature. If you have less weight or height than your friend, you will have less BMR. Moreover, having higher fat mass also lowers BMR in the case of the same body weight. You might have high-fat mass, and your friend might have a high muscle mass (higher muscle mass increases BMR).
You should recalculate your BMR when you notice significant changes in your body weight or when you start a new activity that changes your activity level. Moreover, you should also recalculate your BMR when you hit a plateau during weight gain or weight loss.
Yes, fasting affects the BMR. Fasting for shorter periods increases the body’s basal metabolic rate. However, if you fast for a prolonged period, the body decreases BMR to preserve energy.
BMR or basal metabolic rate is a measure of calories that your body needs to perform basic life-sustaining functions such as circulation, breathing, cellular processes, nerve functions, and digestion. Measuring BMR is a foundational step in your health and fitness journey.
BMR is a personalized metric that differs for everyone. You can determine your total daily energy expenditure (TDEE) with the help of BMR when combined with activity levels. This way, you can keep an estimate of how many calories your body needs and how many calories you consume per day.
BMR and TDEE help you make informed decisions about your nutrition, fitness goals, and lifestyle for sustainable results. In case of any queries, consult a registered healthcare professional to seek medical advice and personalized guidance.