BMR Calculator: Find Your Basal Metabolic Rate
Our BMR calculator estimates how many calories your body burns at complete rest in one day. It works as a basal metabolic rate calculator with three formulas side by side for an easy comparison. Enter your age, sex, height and weight in metric or US units.
What Your BMR Means
Basal metabolic rate is the energy your body needs to stay alive while you lie still all day. It keeps your heart beating, your lungs working and your brain running. For most adults it makes up about 60 to 70 percent of the calories they burn in a day.
A BMR calculator gives you that floor, the number your body spends before you even get out of bed. It leaves out walking, exercise and the energy used to digest food. A resting metabolic rate calculator gives almost the same figure, since RMR reads only slightly higher.
How to Use the BMR Calculator
Pick metric or US units, then enter your sex, age, weight and height. Add your body fat percentage if you know it from a scan or a smart scale. The basal metabolic rate calculator updates as you type.
- Mifflin St Jeor gives the main result in the large box.
- Katch McArdle appears only when you enter body fat.
- The last box shows calories burned per hour at rest.
Working Out Your BMR by Hand
If you want to know how to calculate BMR without a tool, you only need four numbers. Weight goes in kilograms, height in centimeters and age in whole years. Each formula below is exactly what the basal metabolic rate calculator runs behind the scenes.
Mifflin St Jeor Equation
Men use 10 × weight + 6.25 × height − 5 × age + 5. Women use the same terms but end with − 161 instead of + 5. A man aged 30 who weighs 70 kg and stands 175 cm tall gets 700 + 1,093.75 − 150 + 5, which rounds to 1,649 kcal a day.
A woman aged 35 at 62 kg and 165 cm gets 1,315 kcal. A Mifflin St Jeor calculator saves you the arithmetic, but the hand method shows where each number comes from. Height and weight push BMR up, while age pulls it down.
Revised Harris Benedict Equation
For men it is 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age. For women it is 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age. The same man comes out at 1,696 kcal and the woman at 1,381 kcal.
Katch McArdle Equation
Katch McArdle ignores sex and age and works from lean body mass instead. The formula is 370 + 21.6 × lean mass in kg. At 70 kg and 15 percent body fat, lean mass is 59.5 kg and BMR is 1,655 kcal.
Which Formula Should You Trust?
A 2005 review in the Journal of the American Dietetic Association found that Mifflin St Jeor landed within 10 percent of measured values for more people than other formulas. That is why it is the default result on this basal metabolic rate calculator. A Harris Benedict calculator tends to read a little higher, so treat it as a second opinion.
What Changes Your BMR
- Muscle burns more energy at rest than fat does.
- BMR drops slowly after early adulthood, mostly from muscle loss.
Women usually carry less lean mass than men of the same size, so a BMR calculator for women gives a lower figure. Strength training twice a week helps protect your BMR as you age. Crash diets do the opposite and can shrink it along with your muscle.
Using Your BMR Number
The number from a basal metabolic rate calculator is the base for every calorie plan. Multiply it by an activity factor to get your total daily burn, which our Calorie Calculator does for you. Avoid eating below your BMR for long periods without medical advice. Try the tool above and find your number now.
Frequently asked questions
How to calculate BMR quickly?
Use the Mifflin St Jeor formula above with your weight, height and age.
Is a resting metabolic rate calculator the same thing?
Nearly, since RMR usually reads only a few percent higher than BMR.
Does the basal metabolic rate calculator work in pounds?
Yes, switch to US units to enter pounds, feet and inches.
Is there a separate BMR calculator for women?
No, pick female and the tool uses the female version of each formula.
Can a Mifflin St Jeor calculator be wrong?
Yes, it can miss by 10 percent or more for very lean or very heavy people.
Why would I use a Harris Benedict calculator?
It gives a second estimate to compare with Mifflin St Jeor.
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