BMR Calculator

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain essential life functions like breathing, circulation, cell production, and temperature regulation. It typically accounts for 60-75% of your total daily calorie expenditure. Knowing your BMR is important because it establishes the minimum calories your body needs, serves as the foundation for calculating total calorie needs (TDEE), and helps you set safe calorie targets for weight management.

Our calculator uses two scientifically validated formulas. The Mifflin-St Jeor equation (most accurate for most adults): for men, BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 5; for women, BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. The Harris-Benedict equation (revised 1984) provides an alternative estimate. Both require your weight, height, age, and gender. The average of both formulas gives you a reliable estimate.

Several factors influence your BMR: Age (BMR decreases about 1-2% per decade after age 20), Gender (men typically have 5-10% higher BMR due to more muscle mass), Body composition (muscle burns more calories at rest than fat), Body size (larger bodies require more energy), Genetics (can account for up to 10% variation), Hormones (thyroid function significantly impacts BMR), and Environmental temperature (cold environments slightly increase BMR). You cannot change some factors, but building muscle through strength training is the most effective way to raise your BMR.

Eating below your BMR for extended periods is generally not recommended. Your BMR represents the minimum energy your body needs for basic survival functions. Chronically under-eating can lead to muscle loss, metabolic slowdown (adaptive thermogenesis), nutrient deficiencies, hormonal disruptions, fatigue, and weakened immune function. For weight loss, calculate your TDEE (BMR x activity factor) and create a moderate deficit of 500-750 calories below TDEE, not below BMR.