What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just to keep basic functions running. This includes breathing, circulation, cell production, protein synthesis, and ion transport. Your BMR represents the minimum amount of energy your body needs to survive without any physical activity. It accounts for approximately 60 to 75 percent of the total calories most people burn each day.
What Is TDEE?
Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day, accounting for your activity level. TDEE is calculated by multiplying your BMR by an activity multiplier. A sedentary person who sits at a desk all day has a TDEE approximately 1.2 times their BMR. A lightly active person (1-3 days of exercise per week) has a TDEE of approximately 1.375 times their BMR. A moderately active person (3-5 days per week) has a TDEE of approximately 1.55 times their BMR. Very active individuals (6-7 days per week) have a TDEE of approximately 1.725 times their BMR, and extremely active people (physical jobs plus daily exercise) have a TDEE of approximately 1.9 times their BMR.
The Mifflin-St Jeor Equation
The Mifflin-St Jeor equation, developed in 1990, is the most accurate formula for estimating BMR in most adults and is the preferred equation of the American Dietetic Association. The formula for men is: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5. The formula for women is: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161. The only difference between the formulas is the constant at the end — plus 5 for men and minus 161 for women.
The older Harris-Benedict equation (1919) is also widely used but is generally considered less accurate than Mifflin-St Jeor for modern populations. Our calculator uses Mifflin-St Jeor for the most reliable estimate.
Using TDEE for Weight Management
Understanding your TDEE gives you a precise target for calorie intake depending on your goals. To maintain your current weight, eat approximately your TDEE. To lose weight at a rate of approximately one pound per week, eat 500 calories below your TDEE (a deficit of 3,500 calories per week equals approximately one pound of fat loss). To gain weight or muscle, eat 300 to 500 calories above your TDEE. These are starting estimates — actual results vary based on individual metabolism, adherence, and other factors.
Factors That Affect Your BMR
Several factors influence your basal metabolic rate beyond the variables in the formula. Muscle mass significantly increases BMR — muscle tissue burns more calories at rest than fat tissue, which is why strength training is an effective long-term weight management strategy. Age decreases BMR by approximately 1 to 2 percent per decade after age 20 due to muscle loss and hormonal changes. Genetics account for approximately 40 percent of the variation in BMR between individuals. Thyroid function directly regulates metabolic rate — hypothyroidism lowers BMR while hyperthyroidism raises it.
How to Use Our Free BMR Calculator
Our free BMR calculator at cookiescursor.com uses the Mifflin-St Jeor equation to calculate your BMR and TDEE instantly. Enter your age, gender, height, weight, and activity level in either Imperial or Metric units. The results show your BMR, your TDEE at your selected activity level, and calorie targets for weight loss, maintenance, and weight gain. This tool is for informational purposes only — consult a registered dietitian or healthcare professional for personalized nutrition advice.
Frequently Asked Questions
How accurate is the Mifflin-St Jeor equation?
Studies show it predicts RMR within 10% for most non-obese adults. It is the most validated equation for general use but is still an estimate — individual metabolic rates vary.
Why is my TDEE different from what I expected?
Most people underestimate their calorie intake and overestimate their activity level. The activity multipliers assume consistent, sustained exercise — not just occasional activity.
Should I eat below my BMR to lose weight?
Eating below your BMR is generally not recommended without medical supervision. Very low calorie diets can cause muscle loss, nutrient deficiencies, and metabolic adaptation that makes long-term weight loss harder.
Does BMR change when I diet?
Yes. Prolonged calorie restriction causes adaptive thermogenesis — your body reduces its metabolic rate in response to lower food intake. This is why weight loss often slows over time even with consistent calorie restriction.
How is BMR different from RMR?
Resting Metabolic Rate (RMR) is measured under less strict conditions than BMR (which requires complete rest after fasting). RMR is typically 10-20% higher than BMR and is what most online calculators actually estimate.
Can exercise increase my BMR?
Yes, indirectly. Strength training builds muscle mass, which increases BMR over time. High-intensity exercise also causes excess post-exercise oxygen consumption (EPOC), elevating metabolism for hours after a workout.
Calculate Your BMR and TDEE Now
Use our free BMR calculator to find your daily calorie needs instantly. For informational purposes only. No signup required.
