BMR Calculator
0 calories/day at complete rest
What BMR Actually Measures
Basal Metabolic Rate is the number of calories your body burns in 24 hours doing nothing but staying alive — breathing, circulating blood, maintaining body temperature, and running basic cell repair, measured in a fasted state at complete rest. By default this calculator uses the Mifflin-St Jeor equation (10 × weight in kg + 6.25 × height in cm - 5 × age + 5 for men, or -161 for women), which has been shown in validation studies to be the most accurate predictive formula for most adults. The Revised Harris-Benedict equation is an older alternative that tends to run slightly higher. If you know your body fat percentage from a reliable method, the Katch-McArdle formula (370 + 21.6 × lean body mass in kg) can be more accurate because it's based on lean mass rather than total weight, which matters more for very muscular or very lean individuals.
BMR Is a Starting Point, Not a Diet Plan
BMR alone understates how many calories you actually burn in a day, since it excludes digestion, movement, and exercise entirely. The activity-level rows above multiply your BMR by standard factors (1.2 to 1.9) to estimate that fuller number, known as Total Daily Energy Expenditure (TDEE) or maintenance calories. If you're trying to lose or gain weight, use the TDEE calculator or calorie calculator to turn this number into a daily calorie target, and the macro calculator to split that target into protein, carbs, and fat.
A Few Practical Notes
Predictive equations carry a typical margin of error of around 10% versus a lab-measured BMR (indirect calorimetry), and factors like genetics, thyroid function, and muscle mass can shift your real number further. This tool provides an educational estimate only, not medical advice — check with a doctor or registered dietitian before making significant changes to your diet, especially if you have a medical condition or are pregnant or breastfeeding.
Frequently Asked Questions
Which BMR formula should I use?
Mifflin-St Jeor is the default and generally the most accurate for most people, which is why it's selected by default. Use Katch-McArdle instead if you know your body fat percentage from a reliable method (like a DEXA scan or skinfold calipers), since it accounts for lean mass and tends to be more accurate for very muscular or very lean individuals. Revised Harris-Benedict is an older formula included for comparison; it tends to estimate slightly higher than Mifflin-St Jeor.
Is BMR the same as the number of calories I should eat?
No. BMR only reflects calories burned at complete rest and excludes digestion, daily movement, and exercise. To get a realistic daily calorie target, look at the activity-level rows in the results, which multiply your BMR by a standard activity factor to estimate Total Daily Energy Expenditure (TDEE) - that maintenance number, not raw BMR, is the right starting point for weight loss or gain planning.