BMR Calculator
Calculate Basal Metabolic Rate and daily calorie needs.
How to use BMR Calculator
Select Your Biological Sex
Click the 'Male' or 'Female' radio button at the top of the calculator. This is required because BMR calculations differ between sexes due to body composition variations.
Enter Your Age in Years
Type your age into the 'Age' input field. Use whole numbers only (example: 25, 45, 67). Age significantly affects metabolic rate as metabolism naturally decreases with age.
Input Your Height
Select your preferred unit (cm or inches) from the dropdown, then enter your height in the 'Height' field. Example: 175 cm or 5'10". Height is used in the Mifflin-St Jeor equation to calculate BMR.
Enter Your Current Weight
Choose your weight unit (kg or lbs) from the dropdown menu, then input your weight. Example: 75 kg or 165 lbs. Muscle mass and weight directly impact your basal metabolic rate.
Choose Your Activity Level
Select from the 'Activity Level' dropdown: Sedentary, Lightly Active, Moderately Active, Very Active, or Extra Active. This multiplier calculates your Total Daily Energy Expenditure (TDEE) from your BMR.
Click Calculate Button
Press the green 'Calculate BMR' button. Results display instantly below showing your BMR (calories at rest) and TDEE (daily calories burned including activity).
Review Your Results
View your Basal Metabolic Rate in calories/day and your Total Daily Energy Expenditure. Use TDEE for weight loss (subtract 500 calories) or weight gain (add 300-500 calories) calculations.
Related Tools
BMR calculator: find how many calories you burn at rest
BMR calculator: find how many calories you burn at rest
Curious how many calories your body burns just to stay alive? Use ToolHQ's free BMR calculator to find your Basal Metabolic Rate instantly using the most accurate modern formula.
ToolHQ's BMR calculator is a free browser-based tool that calculates the calories your body burns at complete rest using the Mifflin-St Jeor equation, and shows your Total Daily Energy Expenditure (TDEE) across all activity levels.
BMR is the foundation of any calorie management plan. Without knowing your resting burn rate, your calorie targets -- whether for weight loss, maintenance, or muscle gain -- are just guesses.
Key Takeaways
- BMR is the number of calories your body burns at complete rest, with no movement, just to sustain organ function
- The Mifflin-St Jeor equation is the most clinically validated formula for estimating BMR in healthy adults, published in 1990
- For a sedentary person, TDEE is roughly 1.2x BMR -- this is your baseline calorie need for survival without any exercise
- Men's BMR is typically higher than women's of the same weight and height due to higher average muscle mass
- No login or account required -- enter your stats and see your BMR and TDEE instantly
What is BMR and how is it calculated?
BMR stands for Basal Metabolic Rate. It is the number of calories your body needs to perform its most basic life-sustaining functions while at complete rest: breathing, circulating blood, regulating body temperature, and keeping organs functioning.
BMR is not the same as your total daily calorie needs. It doesn't include the calories burned from movement, digestion, or exercise. It is a baseline floor.
The Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition in 1990, calculates BMR as:
- Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
- Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
For a 30-year-old woman who is 165 cm tall and weighs 65 kg: BMR = (10 x 65) + (6.25 x 165) - (5 x 30) - 161 = 650 + 1031.25 - 150 - 161 = 1,370 calories
This means her body burns approximately 1,370 calories per day just to stay alive at rest.
According to the Wikipedia article on Basal Metabolic Rate, several equations exist for estimating BMR, including the older Harris-Benedict (1919) and Katch-McArdle formulas. Research published in the American Journal of Clinical Nutrition has confirmed that Mifflin-St Jeor produces the smallest average error compared to measured resting energy expenditure in both normal-weight and overweight adults, making it the preferred choice for general use.
Why your TDEE matters more than your BMR alone
BMR by itself tells you the minimum. What you actually need to know is your TDEE -- Total Daily Energy Expenditure -- which multiplies your BMR by an activity factor.
Activity multipliers:
- Sedentary (little to no exercise): BMR x 1.2
- Lightly active (light exercise 1-3 days/week): BMR x 1.375
- Moderately active (moderate exercise 3-5 days/week): BMR x 1.55
- Very active (hard exercise 6-7 days/week): BMR x 1.725
- Extra active (very hard daily exercise or physical job): BMR x 1.9
For the example above (1,370 BMR), a lightly active lifestyle gives a TDEE of approximately 1,883 calories. That is her maintenance level. Eating below this causes weight loss; eating above it causes weight gain.
Mini-story: Fatima is a 26-year-old accountant who had been eating around 1,400 calories per day for three months with no weight change. She used the BMR calculator and found her BMR was 1,380 calories. At her activity level (lightly active, occasional evening walks), her TDEE was 1,898 calories. Her 1,400-calorie intake was actually a 498-calorie daily deficit -- enough for slow weight loss. But she had started stress-eating on weekends, which pushed her weekly average to just below her TDEE. Understanding the numbers helped her identify where the gap was closing.
How to use the BMR calculator
- Enter your age in years.
- Select your biological sex. The Mifflin-St Jeor equation uses different constants for men and women.
- Enter your height and weight in your preferred units (metric or imperial).
- View your results. The tool shows your BMR and then TDEE for all five activity levels, so you can quickly identify your maintenance calories for your actual lifestyle.
How BMR changes over time
BMR is not fixed. Several factors cause it to shift:
Age: BMR decreases by roughly 1-2% per decade after age 20, primarily due to gradual loss of muscle mass. This is why many people notice it becomes easier to gain weight in their 30s and 40s even with similar eating habits.
Body composition: Muscle tissue burns more calories at rest than fat tissue. Two people of the same weight and height can have meaningfully different BMRs if one has significantly more muscle mass.
Weight change: As you lose weight, your BMR decreases. This is why calorie targets should be recalculated every 5-10 kg of weight change. Eating the same calories that produced a 0.5 kg/week loss at 90 kg will produce a slower loss at 75 kg.
Mini-story: Ben, a 45-year-old former athlete who had been inactive for several years, was surprised when his BMR calculator result came back at 1,820 calories despite being 85 kg and 180 cm. He had expected a higher number. The calculator helped him understand that his BMR accounted for his age and current body composition, not his former athletic physique. This gave him a realistic starting point for his return to training.
Pair the BMR calculator with ToolHQ's calorie calculator to get personalized daily targets for weight loss, maintenance, and gain based on your BMR. Use the BMI calculator alongside it to see where your weight falls relative to your height. More health and fitness tools are available in the ToolHQ calculator category.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the calories your body burns at complete rest. TDEE adds your activity level on top of BMR. Your TDEE is your actual daily calorie maintenance number -- the amount you need to eat to keep your current weight.
Why is my BMR different from an online calculator I used before?
Different calculators use different equations. The Mifflin-St Jeor (used here) and Harris-Benedict are the two most common. Mifflin-St Jeor is generally considered more accurate for modern populations.
Can I eat just my BMR calories to lose weight?
Eating at your BMR would create a significant deficit for most people, but it is generally not recommended without medical supervision. Very low calorie diets can cause muscle loss, nutrient deficiencies, and metabolic adaptation.
Does BMR account for muscle mass?
Standard BMR equations use weight, height, age, and sex -- not direct body composition measurements. The Katch-McArdle formula accounts for lean body mass directly, which is more accurate if you know your body fat percentage.
What is NEAT and why does it matter for BMR calculations?
NEAT stands for Non-Exercise Activity Thermogenesis -- the calories you burn from everyday movement that isn't formal exercise: fidgeting, standing, walking to meetings, doing household tasks. NEAT varies dramatically between people and explains why two individuals with the same gym schedule, same weight, and same BMR can maintain different weights. Someone with high NEAT (naturally restless, often standing or walking) may burn 300-500 more calories per day than someone who is sedentary outside of exercise. When choosing your activity level in the BMR calculator, think about your total movement throughout the day, not just your gym sessions. A sedentary desk worker who lifts weights three times a week is still often best described as "lightly active" rather than "moderately active" if they sit for most of their waking hours.
How often should I recalculate my BMR?
Recalculate whenever your weight changes by more than 5 kg, after significant lifestyle changes (new job activity level, training program), or if you notice your expected calorie targets are no longer producing the expected results.
The short version
Your BMR is the calories your body burns just to stay alive -- no movement, no exercise counted. Knowing this number is the first step to understanding your total calorie needs. ToolHQ's BMR calculator uses the Mifflin-St Jeor equation to give you your BMR and then shows your TDEE across all five activity levels so you can immediately see your maintenance target.
No guessing, no generic "eat 2,000 calories" advice. Just your number, instantly.
Use it alongside the calorie calculator for weight management targets and the BMI calculator to complete your body metrics picture.