Health & Fitness
BMR Calculator
Find your Basal Metabolic Rate with the Mifflin-St Jeor equation, layer on your activity level, and get a daily calorie target you can actually use.
How it works
Behind the numbers
Your BMR is the energy your body burns at complete rest — breathing, staying warm, keeping your organs running. We use the Mifflin-St Jeor equation, the formula most dietitians consider the most accurate for the general population without lab testing: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, and −161 instead of +5 for women.
BMR alone is not your calorie target, because you don't lie in bed all day. Multiplying by an activity factor — 1.2 for sedentary up to 1.9 for very active — gives TDEE (total daily energy expenditure): the calories that maintain your current weight.
From TDEE we set goal calories: roughly 500 fewer per day for steady fat loss (about a pound a week), or 250–500 more for lean muscle gain. Treat these as starting points — track your weight for two to three weeks and adjust by 100–200 calories if nothing moves.
FAQ
Questions, answered
What is BMR?
Basal Metabolic Rate: the calories your body burns at complete rest to keep you alive. It accounts for roughly 60–70% of most people's daily energy expenditure.
Which BMR formula is the most accurate?
The Mifflin-St Jeor equation (1990) is widely regarded as the most accurate for the general population without clinical testing, and it is the one this calculator uses.
What is the difference between BMR and TDEE?
BMR is your at-rest burn. TDEE (total daily energy expenditure) is BMR multiplied by an activity factor — it is the number of calories that maintains your current weight.
How accurate are online BMR calculators?
Within about 10% for most people. Very muscular individuals, older adults, and people with thyroid or metabolic conditions can differ more — treat the result as a starting point and adjust based on real weight trends.
How often should I recalculate my BMR?
After every 10 lb (5 kg) of weight change, or whenever your activity level changes significantly — a new training program or a desk job both move the number.