Optimitz Logo
Get in Touch

Free BMI Calculator

Calculate your Body Mass Index (BMI) instantly and get personalized health insights. Free, accurate, and used by 100,000+ people monthly.

✓ Instant BMI calculation
✓ Health category insights
✓ No signup required
✓ 100% free forever

Sample BMI Result

See what you'll get instantly

22.5
Normal Weight

Scroll down to calculate your BMI

Calculate

Choose Your Units

Your BMI Result

0.0
-
-

BMI Categories

Underweight Below 18.5
Normal Weight 18.5 - 24.9
Overweight 25.0 - 29.9
Obese 30.0 and above

Health Recommendations

Ready to Track Your Health Journey?

Get the Optimitz app to track your BMI progress, set health goals, and get AI-powered insights.

Get our App - Releasing soon!

More Free Health Calculators

Comprehensive health tools to support your wellness journey

🔥

Calorie Calculator

Get your daily calorie needs and perfect macro breakdown
📊

Body Fat Calculator

Estimate body fat percentage using the US Navy method
⚖️

Ideal Weight Calculator

Find your ideal weight using multiple proven medical formulas
🧬

Protein Calculator

Determine optimal daily protein intake for your goals
💧

Water Intake Calculator

Calculate personalized daily hydration needs
🧠

Stress Level Assessment

Measure your stress levels with the validated PSS-10 scale
😴

Sleep Quality Assessment

Evaluate your sleep quality using the PSQI assessment
🏢

Work-Life Balance Assessment

Assess your work-life balance across 8 key dimensions

Scientific Foundation

Our BMI calculator uses the standard Body Mass Index formula established by the World Health Organization and validated by extensive epidemiological research.

📊 Formula: BMI = weight (kg) / height (m)²

The BMI categories are based on WHO classifications and have been validated across multiple populations and health outcomes.

📚 Key Research Citations
  • World Health Organization (2000). "Obesity: preventing and managing the global epidemic." WHO Technical Report Series 894.
  • Keys et al. (1972). "Indices of relative weight and obesity." Journal of Chronic Diseases, 25(6), 329-343.
  • Garrow & Webster (1985). "Quetelet's index (W/H²) as a measure of fatness." International Journal of Obesity, 9(2), 147-153.
  • Willett et al. (1999). "Guidelines for healthy weight." New England Journal of Medicine, 341(6), 427-434.
⚠️ Clinical Limitations
  • BMI does not distinguish between muscle mass and fat mass
  • May not be accurate for athletes with high muscle mass
  • Different cut-off points may apply to certain ethnic groups
  • Should be used alongside other health assessments for complete evaluation
🎯 Evidence-Based Categories

Our BMI categories are based on WHO classifications linked to mortality and morbidity risk:

  • Underweight (<18.5): Associated with increased mortality risk
  • Normal (18.5-24.9): Optimal health outcomes in population studies
  • Overweight (25-29.9): Slightly increased health risks
  • Obese (≥30): Significantly increased risk of chronic diseases

Last updated: January 2025 | Based on current WHO guidelines and peer-reviewed research