CaclBurn
Get started
BMR Calculator · Day-by-day estimator

BMR Calculator

Find out how many calories your body burns at complete rest. Your Basal Metabolic Rate is the foundation of every calorie and energy calculation — and it takes under 60 seconds to find
  • Home
  • Calculators
  • BMR Calculator
QUICK ANSWER
BMR stands for Basal Metabolic Rate. It is the number of calories your body burns each day at complete rest, with no movement or digestion — essentially what your body needs just to keep you alive. BMR is calculated using the Mifflin-St Jeor equation: for men: (10 x weight in kg) + (6.25 x height in cm) – (5 x age) + 5. For women: (10 x weight in kg) + (6.25 x height in cm) – (5 x age) – 161. The result is expressed in kilocalories per day.
BMR Calculator
Enter your details below to find out how many calories your body burns at complete rest. Results show all three major BMR formulas for comparison.
Your current body weight.
Your height in centimetres.
BMR decreases gradually with age.
Required for Mifflin-St Jeor formula.
If you know your body fat %, enter it here to unlock the Katch-McArdle formula. Leave blank if unsure.
Please fill in weight, height, age and sex before calculating.
BMR Results — Three Formula Comparison
Where Your BMR Calories Go
Your Estimated TDEE at Every Activity Level

What Your BMR Tells You

Your BMR is a useful reference point for understanding your own metabolism and energy needs. Here is what to do with it. Your BMR is not the same as your TDEE (Total Daily Energy Expenditure). BMR only accounts for the energy your body uses at rest. Your actual daily calorie needs are higher because they include the energy used for movement, exercise and digestion. To find your TDEE, your BMR is multiplied by an activity factor that reflects how active you are throughout the day. For most people, BMR makes up roughly 60 to 70 percent of their total daily energy expenditure. This means that even on a completely sedentary day, your body is already burning a significant number of calories just to maintain basic functions. Your BMR is also useful for understanding what happens to your metabolism over time. BMR tends to decrease slightly with age as muscle mass naturally declines. It also changes with significant weight loss or gain. Recalculating your BMR whenever your circumstances change meaningfully gives you an updated baseline to work from. If you want to use your BMR for nutrition planning, the next step is to calculate your TDEE using the TDEE Calculator on this site. Your TDEE is the number that reflects your actual daily energy use and is the appropriate starting point for any calorie or nutrition target.

What is BMR (Basal Metabolic Rate)?

Basal Metabolic Rate is the minimum amount of energy your body requires to sustain its basic physiological functions while at complete rest in a thermoneutral environment. In plain terms, it is how many calories your body burns in a day if you did absolutely nothing except lie still and breathe. These functions include maintaining heart rate and circulation, keeping your body temperature stable, supporting brain and nervous system activity, maintaining organ function including the liver, kidneys and lungs, and cell repair and protein synthesis. BMR is sometimes used interchangeably with RMR (Resting Metabolic Rate), though they are technically different measurements. True BMR is measured under very strict laboratory conditions after at least 12 hours of fasting and a full night of sleep. RMR is measured under less strict conditions and is slightly higher than true BMR. In practice, the terms are often used interchangeably and the difference is small enough that it does not meaningfully affect real-world nutrition planning. Several factors influence your BMR. Body size and composition are the largest factors: larger bodies and bodies with more muscle mass have higher BMRs because there is more tissue for the body to maintain. Age affects BMR because muscle mass tends to decline with age, reducing the body’s resting energy demand. Biological sex influences BMR because males typically have higher muscle mass than females at the same weight and height. Hormonal factors, particularly thyroid function, also play a significant role, which is why thyroid disorders can affect body weight and energy levels.

How is BMR Calculated?
The Mifflin-St Jeor Equation

This calculator uses the Mifflin-St Jeor equation, which was developed in 1990 and has since been validated in multiple independent studies as the most accurate standard formula for estimating BMR in the general population. A 2005 comparison study published in the Journal of the American Dietetic Association by Frankenfield and colleagues compared several BMR prediction equations and found that Mifflin-St Jeor produced the most accurate results for the greatest number of people across different body types and age groups. The formula is: 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 The calculator also shows your BMR calculated using the original Harris-Benedict equation (revised by Roza and Shizgal in 1984) for comparison. The two equations typically produce results within 5 percent of each other for most people. For people who know their body fat percentage, the calculator also shows the Katch-McArdle formula result, which uses lean body mass rather than total weight and can be more accurate for people with very high or very low body fat percentages.

BMR calculator showing calories burned at rest based on age, weight, height, and body composition

BMR Formula Comparison

The table below compares the three most commonly used BMR formulas. All three are included in the calculator above. Mifflin-St Jeor is the default and is recommended for most people.
Formula Published Best For Accuracy
Mifflin-St Jeor 1990 General population. Most validated formula available. Most accurate for majority of people. Recommended default.
Harris-Benedict (revised) 1984 Good general estimate. Slightly less accurate than Mifflin-St Jeor. Accurate within 5 to 10% for most people.
Katch-McArdle 1975 People who know their body fat percentage. Uses lean mass. Most accurate for very lean or very high body fat individuals.
Source: Frankenfield et al. (2005), Journal of the American Dietetic Association. Mifflin MD et al. (1990), American Journal of Clinical Nutrition.

Use Your BMR With These Tools

TDEE Calculator

Convert your BMR into a full daily energy expenditure figure by adding your activity level.
Open Calculator

Body Recomposition Calculator

Use your BMR as the foundation for a fat loss and muscle gain nutrition plan.
Open Calculator

Macro Calculator for Fat Loss

Turn your BMR and TDEE into personalised daily protein, carb and fat targets.
Open Calculator

BMR Calculator
Frequently Asked Questions

What does BMR stand for?

BMR stands for Basal Metabolic Rate. It is the number of calories your body burns each day at complete rest, with no movement or digestion. It represents the minimum energy your body needs to maintain its basic biological functions: breathing, circulation, temperature regulation, organ function and cell repair.

BMR is your calorie burn at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor to account for all movement and exercise throughout the day. TDEE is always higher than BMR. For most people, TDEE is 20 to 60 percent higher than their BMR. When planning nutrition, always use your TDEE rather than your BMR.

BMR varies significantly based on body size, age and sex, so there is no single “good” BMR that applies universally. A higher BMR generally means the body burns more calories at rest, which is typically associated with greater muscle mass and a larger body size. What matters more than the number itself is understanding how your BMR contributes to your total daily energy needs.

This calculator uses the Mifflin-St Jeor equation, which research identifies as the most accurate widely available formula for estimating BMR, accurate to within 5 to 10 percent for most people. Accuracy varies for people at the extremes of body composition, very lean athletes or those with very high body fat, where the Katch-McArdle formula (which uses lean body mass) tends to be more accurate.
Yes. BMR tends to decrease gradually with age, primarily because muscle mass declines as part of the natural ageing process. Muscle tissue is metabolically active, meaning it burns more calories at rest than fat tissue. The rate of BMR decline is typically around 1 to 2 percent per decade after age 30. Regular resistance training, which preserves and builds muscle mass, helps slow this decline.
Yes. When you lose weight, your BMR decreases because there is less tissue for your body to maintain. This is sometimes called metabolic adaptation. It is one reason why weight loss can slow over time even with a consistent calorie deficit. Recalculating your BMR after losing 5 or more kilograms gives you an updated baseline that reflects your new body size.
The most effective way to increase your BMR is to build and maintain muscle mass through resistance training. Muscle tissue burns significantly more calories at rest than fat tissue. Eating adequate protein also helps maintain muscle mass. Beyond these, BMR is largely determined by factors outside your control including age, genetics and body size.
The Katch-McArdle formula calculates BMR using lean body mass (total weight minus fat mass) rather than total body weight. It tends to be more accurate for people whose body composition differs significantly from average, including very lean athletes who may have a higher proportion of muscle, and people with higher body fat who may have a lower lean mass ratio. To use this formula you need to know your body fat percentage.
DISCLAIMER
This calculator provides estimates of Basal Metabolic Rate using published mathematical formulas. Results are for informational purposes only and do not constitute medical or nutritional advice. Individual metabolic rates vary due to factors including genetics, hormonal function and health status. If you have concerns about your metabolism or health, please consult a qualified healthcare professional.