Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions while at complete rest. These functions include breathing, circulation, cell production, nutrient processing, and maintaining body temperature. Your BMR represents the minimum amount of energy needed to keep your body functioning, excluding any physical activity or food digestion.

Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day, including your BMR plus additional calories burned through physical activity, exercise, and the thermic effect of food (digestion). Your TDEE represents your maintenance calorie level—the amount you need to consume to maintain your current weight, assuming your activity level remains constant.

This calculator uses the Mifflin-St Jeor equation, which is considered one of the most accurate formulas for estimating BMR. Studies have shown it to be accurate within 10% of laboratory measurements for most people. However, individual variations in metabolism, muscle mass, genetics, and hormonal factors can affect your actual metabolic rate. Use these calculations as a starting point and adjust based on your personal results and progress toward your goals.

For weight loss, create a calorie deficit by consuming fewer calories than your TDEE. A deficit of 500-1000 calories per day is generally recommended for a weight loss of 1-2 pounds per week, which is considered safe and sustainable. For weight gain or muscle building, consume more calories than your TDEE. A surplus of 250-500 calories is typically sufficient for muscle growth while minimizing fat gain. For weight maintenance, aim to consume calories equal to your TDEE.

It's recommended to recalculate your BMR and TDEE whenever there are significant changes in your body weight, activity level, or age. As a general guideline, recalculate after every 10 pounds of weight change, when you substantially increase or decrease your physical activity, or annually as you age. Regular recalculation ensures your calorie targets remain appropriate for your current body composition and lifestyle.

While there is some individual variation in metabolic rate, most people's BMR falls within 10-15% of the predicted values for their age, weight, height, and gender. True metabolic disorders that significantly affect BMR are relatively rare. Factors that can influence your metabolic rate include muscle mass (more muscle increases BMR), age (metabolism typically slows with age), hormonal health, genetics, and recent dieting history. If you suspect a metabolic issue, consult with a healthcare provider.