BMR Calculator

What is BMR (Basal Metabolic Rate)?

Your Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production, and organ function — while at complete rest. It represents the minimum energy your body requires just to stay alive, without any physical activity factored in.

BMR is the starting point for all calorie calculations. Whether your goal is weight loss, muscle gain, or maintenance, understanding your BMR gives you a scientifically grounded baseline for setting your daily calorie target. Without knowing your BMR, any calorie goal you set is essentially a guess.

How is BMR Calculated?

This calculator uses two clinically validated formulas. The Mifflin-St Jeor equation (1990) is the most accurate for most people and is recommended by the Academy of Nutrition and Dietetics. The older Harris-Benedict equation (revised 1984) tends to slightly overestimate BMR for sedentary individuals.

Example: A 30-year-old male, 75 kg, 175 cm has a Mifflin-St Jeor BMR of approximately 1,794 calories/day. That’s how many calories he’d burn lying still all day doing nothing.

How to Use This BMR Calculator

Select your unit system (metric or imperial), choose your biological sex, and enter your age, weight, and height. Select your preferred formula — Mifflin-St Jeor is recommended for most people. Hit Calculate to see your BMR plus your Total Daily Energy Expenditure (TDEE) across five activity levels so you can find your real daily calorie target.

What Your BMR Result Means

Your BMR is the calories you burn doing absolutely nothing. But nobody does nothing — so your actual daily calorie need (TDEE) is your BMR multiplied by an activity factor. The calculator shows your TDEE across all activity levels so you can match your actual lifestyle. To lose weight: eat below your TDEE. To gain muscle: eat above your TDEE. To maintain: eat at your TDEE.

Is This BMR Calculator Accurate?

BMR formulas are population-based estimates with a margin of error of roughly ±10%. Individual factors not captured by the formula include muscle-to-fat ratio (muscle burns more calories), hormonal conditions like thyroid disorders, medications, genetics, and age-related metabolic changes. For the most accurate measurement, a metabolic test (indirect calorimetry) performed by a healthcare professional is the gold standard. For most people, the Mifflin-St Jeor formula provides a reliable enough estimate to build a nutrition plan around.

How to Choose Your Inputs

Weight: Use your current body weight, not your goal weight. Height: Your actual standing height. Age: BMR decreases with age — roughly 2% per decade after 20 — so accurate age matters. Formula: Mifflin-St Jeor is more accurate for most people, especially those who are overweight or obese. Harris-Benedict tends to slightly overestimate for sedentary individuals but may be more accurate for very athletic people.

Suitable for Women

Yes — the BMR calculator includes a separate formula for women, which accounts for the physiological differences in body composition between biological sexes. Women typically have a lower BMR than men of the same height, weight, and age due to proportionally less lean muscle mass. Women should select “Female” to get an accurate result. Note that BMR during pregnancy or breastfeeding is significantly higher — consult a healthcare provider for personalised guidance in these cases.

Suitable for Men

Yes — the male BMR formula accounts for men’s typically higher muscle mass and metabolic rate. Men with high muscle mass (bodybuilders, athletes) may find their actual calorie needs are higher than the formula estimates, since the formula uses total body weight rather than lean body mass. For highly muscular individuals, a body-composition-adjusted calculation or professional metabolic test will be more accurate.

BMR vs TDEE — What’s the Difference?

BMR is your resting calorie burn — what you’d need if you stayed in bed all day. Total Daily Energy Expenditure (TDEE) is your actual daily calorie burn including all physical activity. TDEE = BMR × Activity Multiplier. The five standard activity levels used are: Sedentary (×1.2), Lightly Active (×1.375), Moderately Active (×1.55), Very Active (×1.725), and Extra Active (×1.9). Your TDEE is the number you use for calorie planning — not your BMR.

How to Use Your BMR for Weight Loss or Muscle Gain

Find your TDEE at your actual activity level. For weight loss, create a calorie deficit of 300–500 calories below your TDEE — this produces roughly 0.3–0.5 kg of fat loss per week without sacrificing too much muscle. For muscle gain, eat 200–300 calories above your TDEE in a lean bulk. For maintenance, eat at your TDEE. Never eat below your BMR for extended periods — this starves essential bodily functions and causes muscle loss.

Frequently Asked Questions