BMR Calculator -- Basal Metabolic Rate

The Basal Metabolic Rate (BMR) represents the total number of calories your body requires to perform basic, life-sustaining functions such as breathing, circulation, and cell production while completely at rest. The Mifflin-St Jeor equation (1990) is the standard formula, calculated as 10×Weight(kg) + 6.25×Height(cm) - 5×Age(years) + 5 for men, and subtracting 161 for women. This model is favored because the older Harris-Benedict formula (1919) tends to overestimate resting metabolism by approximately 5%. BMR is heavily influenced by age and body composition; naturally, BMR decreases by 1% to 2% per decade after age

• Conversely, muscle tissue is highly metabolically active, burning roughly three times more calories than fat tissue at rest. Therefore, increasing lean muscle mass through resistance training is one of the most effective strategies to elevate your baseline BMR.

How to Use This Calculator

Enter your Biological Sex — select from Male, Female, Age (e.g. 30 in years), Height (e.g. 175 in cm), Weight (e.g. 75 in kg), and Activity Level — select from Sedentary (desk job, no exercise), Lightly Active (1-3 days/week), Moderately Active (3-5 days/week). Results update instantly — no submit button needed. Use metric or imperial units as labeled. For the most accurate result, measure height and weight in the morning without shoes.

The Formula

Mifflin-St Jeor: Male BMR = 10W + 6.25H - 5A + 5

Female BMR = 10W + 6.25H - 5A - 161

TDEE = BMR × Activity Multiplier (1.2 to 1.9)

Worked Example

Male, 30 yrs, 175 cm, 75 kg, moderately active: BMR =+-+5 = 750+1093.75-150+5 = 1,698.75 kcal. TDEE = 1,699 × 1.55 = 2,633 kcal/day.

Understanding Your Result

Your BMR is the calories burned at complete rest — your TDEE (Total Daily Energy Expenditure) adds activity. To lose 1 lb/week, create a 500 kcal/day deficit. To lose 2 lbs/week, a 1,000 kcal/day deficit is required — this is generally the safe maximum recommended by clinicians. Below 1,200 kcal/day for women or 1,500 kcal/day for men risks metabolic adaptation and nutrient deficiencies. Protein intake of 1.6–2.2 g/kg body weight preserves muscle during a caloric deficit.