BMR Calculator
Calories your body burns at complete rest using the Mifflin-St Jeor equation. The foundation of any meal plan.
Basal Metabolic Rate (BMR)
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Calories burned at complete rest to maintain vital functions.
Why BMR matters
BMR is the foundation of every calorie calculation. It is the number of calories your body would burn if you stayed in bed all day, did not eat, and did not move. Even at complete rest, your body needs significant energy to keep your heart beating, lungs breathing, brain thinking, and cells maintaining themselves.
BMR typically accounts for 60 to 70 percent of total daily energy expenditure in sedentary people. Understanding your BMR helps you set realistic calorie targets. If your BMR is 1600, eating below that for an extended period is rarely sustainable.
The Mifflin-St Jeor equation
The Mifflin-St Jeor equation was published in 1990 and is currently considered the most accurate BMR formula for most people. It improved on the older Harris-Benedict equation, which tended to overestimate BMR by about 5 percent.
For men: BMR equals 10 times weight in kilograms plus 6.25 times height in centimeters minus 5 times age in years plus 5. For women, the same formula minus 161. The gender offset reflects differences in lean mass at the same weight.
How to use BMR
BMR alone is not your daily calorie target. It is the floor. To get your actual daily energy needs, multiply BMR by an activity factor (1.2 for sedentary, up to 1.9 for extreme athletes) to get TDEE.
A common mistake is eating below BMR to lose weight faster. This rarely works long term because the body adapts by reducing metabolic rate. A more sustainable approach is a modest deficit from TDEE while keeping intake at or above BMR.
Frequently asked questions
Quick answers to the most common questions about this calculator.
Should I eat below my BMR to lose weight?+
Generally no. Eating below BMR for extended periods causes metabolic adaptation and muscle loss. A better approach is a modest deficit from your TDEE while keeping intake at or above BMR.
Why does my BMR decrease as I age?+
BMR drops about 1 to 2 percent per decade after age 20, mostly due to loss of lean muscle mass. Resistance training is the most effective way to slow this decline.
Which BMR formula is most accurate?+
Mifflin-St Jeor is currently the most accurate for most people. Katch-McArdle, which uses lean body mass, is more accurate for muscular individuals but requires knowing your body fat percentage.