Calculate your Body Mass Index (BMI) to assess whether your weight is in a healthy range for your height. This tool uses the standard formula recommended by the World Health Organization.
Body Mass Index (BMI) is a widely used screening tool that measures body fat based on height and weight. Developed in the 19th century by Belgian mathematician Adolphe Quetelet, BMI has become a standard method for assessing weight categories that may lead to health problems. According to the Centers for Disease Control and Prevention, BMI provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health issues.
The BMI formula is simple: weight in kilograms divided by height in meters squared (kg/m²). For imperial measurements, the formula is (weight in pounds × 703) divided by height in inches squared. Our calculator automatically handles both conversions, providing accurate results regardless of your preferred measurement system.
| BMI Category | BMI Range | Health Risk | Recommendations |
|---|---|---|---|
| Underweight | Below 18.5 | Increased risk of nutritional deficiencies, osteoporosis, and weakened immune system | Consult with a healthcare provider to develop a healthy weight gain plan with proper nutrition |
| Normal Weight | 18.5 - 24.9 | Lowest health risk; associated with optimal health outcomes | Maintain current weight through balanced diet and regular physical activity |
| Overweight | 25 - 29.9 | Increased risk for hypertension, type 2 diabetes, and cardiovascular diseases | Moderate weight loss (5-10% of body weight) through diet and exercise improvements |
| Obesity Class I | 30 - 34.9 | High risk for multiple health conditions including sleep apnea and certain cancers | Comprehensive weight management program; medical consultation recommended |
| Obesity Class II | 35 - 39.9 | Very high risk; significantly reduced life expectancy | Medical intervention likely necessary; supervised weight loss programs |
| Obesity Class III | 40 and above | Extremely high risk for life-threatening conditions | Immediate medical attention required; potential surgical interventions |
While BMI is a useful screening tool, it has several limitations that are important to understand:
For a more comprehensive assessment, healthcare providers often use additional measurements like waist circumference, waist-to-hip ratio, and body composition analysis. The National Heart, Lung, and Blood Institute recommends using BMI as a starting point for weight assessment.
Whether your goal is weight loss, weight gain, or weight maintenance, here are evidence-based strategies:
For most adults, a healthy BMI falls between 18.5 and 24.9. However, individual factors like age, muscle mass, and ethnicity should be considered. The World Health Organization provides detailed guidelines for different populations.
BMI can be misleading for athletes and bodybuilders who have high muscle mass. They may register as overweight or obese despite having low body fat. Additional assessments like body fat percentage measurements are more appropriate for these individuals.
No, children and teens require different BMI assessments that account for age and gender-specific growth patterns. Pediatricians use BMI-for-age percentiles rather than the standard adult categories.
For most people, checking BMI every 1-3 months is sufficient for tracking trends. However, daily weight fluctuations are normal and don't necessarily reflect fat loss or gain. Focus on long-term trends rather than day-to-day changes.
Explore our other health and fitness calculators to get a more complete picture of your health:
Medical Disclaimer: This BMI calculator is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read on this website.