BMR Calculator

What is BMR Calculator?

A BMR calculator estimates your Basal Metabolic Rate — the minimum calories your body needs to function at rest. Understanding your BMR is the foundation for any diet, fitness, or weight management plan because it tells you how many calories you burn just by existing. Our calculator supports three scientifically validated formulas: Mifflin-St Jeor (most accurate for general use), Harris-Benedict (classic formula), and Katch-McArdle (body fat-based). It also shows your TDEE at five activity levels and goal calories for weight loss, maintenance, or gain.

How It Works

Enter your age, gender, height, weight, and optionally body fat percentage. Select a formula (Mifflin-St Jeor is recommended). The calculator computes your BMR and then multiplies it by activity factors to show TDEE at each level. Goal calories are calculated as TDEE ± 500 calories for moderate weight change.

Formula

Mifflin-St Jeor:
Male: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Female: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

Harris-Benedict:
Male: 88.362 + (13.397 × weight) + (4.799 × height) − (5.677 × age)
Female: 447.593 + (9.247 × weight) + (3.098 × height) − (4.330 × age)

Katch-McArdle: 370 + (21.6 × lean body mass kg)

Formula Explained

All formulas estimate resting energy expenditure using body metrics. Mifflin-St Jeor (1990) is the most recent and accurate. Harris-Benedict (1919, revised 1984) tends to overestimate by 5–15%. Katch-McArdle ignores sex and age, using only lean mass — more accurate for athletic individuals who know their body fat percentage.

Example

Male, 30 years, 75 kg, 175 cm Mifflin-St Jeor: (10×75) + (6.25×175) − (5×30) + 5 = 1,693 cal/day TDEE: Sedentary: 1,693 × 1.2 = 2,032 Moderately Active: 1,693 × 1.55 = 2,624 Very Active: 1,693 × 1.725 = 2,920 Goal calories (moderate activity): Weight loss: 2,124 cal/day Maintain: 2,624 cal/day Weight gain: 3,124 cal/day

Tips & Best Practices

✓Use Mifflin-St Jeor as your default — it is the most validated formula.
✓If you know your body fat %, try Katch-McArdle for a more personalized result.
✓Never eat below your BMR for extended periods — it can slow your metabolism.
✓Recalculate every 5–10 lbs of weight change as your BMR shifts.
✓Activity level is the most subjective part — be honest about your exercise frequency.

Common Use Cases

•Determining daily calorie needs for weight loss or gain
•Setting up a macro-based nutrition plan
•Understanding how exercise affects total energy expenditure
•Comparing BMR formulas for personalized accuracy
•Planning diet strategies for fitness and body composition goals

Frequently Asked Questions

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell production, and brain function. It represents about 60–75% of your total daily energy expenditure. Think of it as the calories you would burn if you stayed in bed all day.

The Mifflin-St Jeor equation (1990) is considered the most accurate for healthy adults and is recommended by the Academy of Nutrition and Dietetics. It is within 10% of measured BMR for most people. Katch-McArdle is more accurate for athletic individuals when body fat percentage is known.

TDEE (Total Daily Energy Expenditure) is your total calories burned per day including all activity. It equals BMR × Activity Factor. Sedentary (desk job, no exercise) uses 1.2×. Moderately active (3–5 workouts/week) uses 1.55×. Very active (daily intense exercise) uses 1.725×.

For safe weight loss, eat 500 calories below your TDEE to lose about 1 pound (0.45 kg) per week. A 1,000 calorie deficit leads to ~2 pounds per week, but going below 1,200 cal (women) or 1,500 cal (men) is generally not recommended without medical supervision.