BMR Calculator - Free Basal Metabolic Rate and TDEE Calculator for Daily Calorie Needs and Weight Management

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, and cell production. It represents 60-75% of your total daily calorie expenditure. BMR does not include calories burned through physical activity or digesting food. For example, a 30-year-old male weighing 180 lbs might have a BMR of 1,800 calories, meaning his body burns 1,800 calories per day even if he stays in bed all day.

TDEE (Total Daily Energy Expenditure) is the total number of calories you burn per day, including BMR plus physical activity, exercise, and food digestion (thermic effect). TDEE = BMR × Activity Multiplier. For example, if your BMR is 1,800 calories and you're moderately active (exercise 3-5 days/week), your TDEE would be 1,800 × 1.55 = 2,790 calories per day. TDEE is the number you should use for setting calorie goals, not BMR.

The Mifflin-St Jeor equation is generally more accurate for modern populations and is recommended by most nutritionists. It was developed in 1990 and accounts for changes in body composition and lifestyle compared to the original Harris-Benedict equation from 1919. Studies show Mifflin-St Jeor has a 5-10% accuracy advantage, especially for people who are overweight or obese. However, both formulas provide reasonable estimates within 200-300 calories of measured BMR.

To lose weight safely, create a calorie deficit of 500 calories per day, which results in approximately 1 pound (0.5 kg) of weight loss per week. Calculate your TDEE first, then subtract 500 calories. For example, if your TDEE is 2,500 calories, eat 2,000 calories per day. Never eat below your BMR or less than 1,200 calories (women) or 1,500 calories (men) without medical supervision, as this can slow metabolism and cause nutrient deficiencies.

Choose your activity level honestly: Sedentary (desk job, no exercise) = 1.2x BMR, Light (exercise 1-3 days/week) = 1.375x, Moderate (exercise 3-5 days/week) = 1.55x, Active (exercise 6-7 days/week) = 1.725x, Very Active (physical job + daily exercise) = 1.9x. Most people overestimate their activity level. If you sit at a desk all day and go to the gym 3 times per week for 45 minutes, you're 'Light' or 'Moderate' at most, not 'Active'. Track your weight for 2-3 weeks and adjust if needed.

Yes, BMR changes based on age, weight, muscle mass, and hormones. BMR naturally decreases by 1-2% per decade after age 20 due to muscle loss and hormonal changes. Building muscle increases BMR by 6-10 calories per pound of muscle gained. Losing weight decreases BMR because a smaller body requires fewer calories. Extreme dieting can temporarily lower BMR by 15-20% (metabolic adaptation). Recalculate your BMR every 10-15 pounds of weight change or yearly.

Macronutrients are protein, carbohydrates, and fats - the three main nutrients that provide calories. A balanced split is 30% protein, 40% carbs, 30% fats. Protein (4 cal/g) builds and repairs muscle; aim for 0.7-1g per pound of body weight. Carbohydrates (4 cal/g) provide energy for workouts and brain function. Fats (9 cal/g) support hormones and nutrient absorption. Athletes may use 40% carbs / 30% protein / 30% fats. Keto dieters use 5% carbs / 25% protein / 70% fats. Adjust based on your goals and preferences.