BMR & TDEE Calculator

Understanding BMR and TDEE

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — just to keep vital organs functioning, maintain body temperature, and support basic cellular processes. It represents the minimum energy your body needs to survive. Your Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor, giving you the total calories you burn in a typical day including all physical activity. For weight management, TDEE is the more useful number because it represents your actual daily calorie needs. Eating below your TDEE creates a calorie deficit for weight loss; eating above creates a surplus for weight gain.

Mifflin-St Jeor vs Harris-Benedict

The Mifflin-St Jeor equation, published in 1990, is considered the most accurate BMR formula for most people and is recommended by the Academy of Nutrition and Dietetics. The Harris-Benedict equation, originally published in 1919 and revised in 1984, was the standard for decades but tends to overestimate BMR by about 5%. The Katch-McArdle formula uses lean body mass instead of total weight, making it more accurate for people who know their body fat percentage. For most people, Mifflin-St Jeor provides the best starting estimate.

How Activity Multipliers Work

The activity multiplier converts your BMR to TDEE by accounting for daily physical activity. A sedentary person (desk job, no exercise) multiplies by 1.2, adding 20% to their BMR. A very active person multiplies by 1.725, nearly doubling their calorie needs. The most common mistake is overestimating activity level — most people with office jobs who exercise 3 times per week are "lightly active" (1.375), not "moderately active" (1.55). Being honest about your activity level is crucial for accurate calorie calculations.

Calorie Deficit for Weight Loss

A deficit of 500 calories per day below your TDEE results in approximately 0.5 kg (1 lb) of weight loss per week. A 1,000 calorie deficit leads to about 1 kg per week. However, deficits larger than 500 calories should be supervised by a healthcare professional. Very low calorie diets (below 1,200 for women or 1,500 for men) can cause nutrient deficiencies, muscle loss, metabolic adaptation, and other health issues. Sustainable weight loss comes from moderate deficits maintained over time, not extreme restriction.

Macronutrients Explained

Protein provides 4 calories per gram and is essential for muscle repair, immune function, and satiety. A common recommendation is 1.6–2.2g per kg of body weight for active individuals. Carbohydrates provide 4 calories per gram and are the body's preferred fuel source. Fat provides 9 calories per gram and is vital for hormone production, vitamin absorption, and brain function. A balanced macronutrient ratio of 30% protein, 40% carbohydrates, and 30% fat works well for most people, though individual needs vary based on activity type, health conditions, and goals.