BMR Calculator — Free 2026
Estimate your basal metabolic rate using three trusted formulas — Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle — free, instant, no sign-up.
Your BMR Results (cal/day)
How It Works
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Understanding Basal Metabolic Rate
Your basal metabolic rate (BMR) is the foundation of your daily energy expenditure. It represents the minimum number of calories your body needs to sustain vital functions — breathing, blood circulation, brain activity, cell production, and body temperature regulation — while completely at rest. For most people, BMR accounts for roughly 60 to 75 percent of total daily calorie burn, making it the single largest component of energy expenditure. Understanding your BMR is the first step toward building an effective nutrition plan, whether your goal is weight loss, muscle gain, or maintenance.
The Three BMR Formulas Compared
The Mifflin-St Jeor equation, published in 1990, is widely regarded as the most accurate for the general population. The American Dietetic Association recommends it as the preferred method for estimating BMR. For men the formula is 10 times weight in kg plus 6.25 times height in cm minus 5 times age plus 5. For women, the same formula applies but with minus 161 instead of plus 5.
The Harris-Benedict equation, originally published in 1919 and revised in 1984, is one of the oldest and most well-known BMR formulas. It tends to overestimate BMR by about 5 percent compared to Mifflin-St Jeor, particularly in overweight individuals. Despite this, it remains commonly used in clinical settings.
The Katch-McArdle formula takes a different approach by using lean body mass rather than total weight. This makes it potentially more accurate for athletes and individuals with known body fat percentages, since it accounts for the metabolic difference between muscle and fat tissue. The formula is 370 plus 21.6 times lean body mass in kilograms. You can estimate your lean body mass using our lean body mass calculator or body fat calculator.
From BMR to TDEE
BMR alone does not tell you how many calories to eat. To find your total daily energy expenditure (TDEE), you multiply BMR by an activity factor: 1.2 for sedentary individuals, 1.375 for light exercise one to three days per week, 1.55 for moderate exercise three to five days, 1.725 for heavy exercise six to seven days, and 1.9 for very heavy exercise or a physical job. TDEE gives you the actual number of calories you burn each day and serves as the baseline for setting calorie targets for weight management.
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