Free BMR Calculator
Enter your weight, height, age and gender to instantly calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation. Get your TDEE for weight loss, muscle gain, or maintenance.
Metabolic Parameters
Input your biometric data to synthesize your caloric baseline.
FORMULA: BMR = 10×70 + 6.25×170 - 5×25 + 5What Is BMR?
Your Basal Metabolic Rate (BMR)is the number of calories your body burns just to stay alive — breathing, keeping your heart beating, regulating temperature, and repairing cells. This happens even when you are sleeping or lying completely still. It is your body's minimum fuel requirement.
BMR is the foundation of every diet and fitness plan. Without knowing it, calorie targets for weight loss or muscle gain are just guesswork. This calculator uses the Mifflin-St Jeor equation — the formula recommended by the American Dietetic Association as the most accurate for modern adults, with ±10% accuracy for 82% of people.
BMR vs TDEE: What's the Difference?
BMR is what you burn at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by your activity level — the real number to hit for weight maintenance.
The Mifflin-St Jeor Formula
Our calculator applies this formula automatically once you enter your stats.
How to Use Your BMR Result
Lose Weight
Eat 300–500 kcal below your TDEE daily. This creates a sustainable deficit of ~0.5 kg per week without crashing your metabolism.
Gain Muscle
Eat 250–400 kcal above your TDEE. Combined with resistance training, this fuels lean mass growth with minimal fat gain.
Maintain Weight
Match your calories exactly to your TDEE. This is the target for athletes in their off-season or anyone happy with their current body composition.
Accuracy & Limitations
The Mifflin-St Jeor formula is the most validated BMR equation for general adults, but it does not account for body composition. Athletes with high muscle mass will typically have a higher real BMR than calculated. For a fuller picture, pair this with our BMI Calculator, the Ideal Weight Calculator, and the Water Intake Guide. No health data you enter is ever stored, sent to a server, or logged.
Common Questions
BMR decreases with age. An average 25-year-old male has a BMR around 1,800–1,900 kcal/day; a 50-year-old around 1,600–1,700. Women average 10–15% lower. Your individual stats matter more than age-based averages.
BMR is how many calories you burn doing nothing. TDEE is your actual daily burn — BMR multiplied by your activity level. To lose weight, eat below TDEE. To gain muscle, eat above TDEE.
Subtract 300–500 calories from your TDEE. This creates a safe deficit, leading to around 0.3–0.5 kg of fat loss per week without muscle loss or metabolic slowdown.
Men generally have more lean muscle mass, which burns more calories at rest. The +5 vs −161 constant in the Mifflin-St Jeor formula accounts for this biological difference in resting metabolism.
It is within ±10% of true resting metabolic rate for about 82% of people. Athletes with very high muscle mass may find their true BMR is higher than predicted.
This is strongly not recommended. Eating below BMR long-term can cause muscle loss, hormonal disruption, and metabolic adaptation where your body becomes more efficient at storing fat.
No. All calculations happen instantly inside your browser. No weight, height, age, or gender data is ever sent to our servers, stored in a database, or logged in any form.