Free BMI Calculator
Calculate your Body Mass Index using standard BMI formulas. Supports both metric (kilograms/centimeters) and imperial (pounds/inches) measurements. See your BMI category and healthy weight range for your height.
What Is BMI?
Body Mass Index (BMI) is a simple measurement that estimates your body fat based on your height and weight. It is widely used by healthcare professionals as a screening tool to identify potential weight categories that may lead to health problems. While BMI does not directly measure body fat, research shows it correlates moderately with direct body fat measurements.
How BMI Is Calculated
BMI uses the same formula for all adults. The standard formulas are:
- Metric formula: BMI = weight (kg) / height (m)²
- Imperial formula: BMI = (weight (lbs) / height (in)²) × 703
Our calculator handles both systems automatically. Simply enter your weight and height in any unit, and your BMI and weight category appear instantly.
BMI Categories for Adults
The World Health Organization (WHO) defines the following BMI categories for adults aged 20 and older:
- Below 18.5: Underweight — may indicate malnutrition, an eating disorder, or other health conditions
- 18.5 – 24.9: Normal weight — lowest health risk for most individuals
- 25.0 – 29.9: Overweight — increased risk for heart disease, high blood pressure, and type 2 diabetes
- 30.0 and above: Obese — significantly increased health risk; higher BMI within this range correlates with greater risk
These ranges apply to most adults but may not be accurate for athletes, pregnant women, older adults, or children. Our tool provides the standard WHO classification for reference.
Features
- Metric and imperial unit support with automatic conversion
- Instant BMI category classification from underweight to obese
- Healthy weight range display for your specific height
- Visual BMI scale with color-coded categories for easy interpretation
- No data uploads — all calculations happen locally in your browser
Limitations of BMI
While BMI is a useful screening tool, it has important limitations. It does not distinguish between muscle and fat mass, so muscular individuals may be misclassified as overweight or obese. It also does not account for bone density, body composition, fat distribution, age, sex, or ethnicity. Waist circumference and other measurements can provide additional context. Always consult a healthcare provider for a complete health assessment.
Who Should Use This Tool
Our BMI calculator is ideal for anyone who wants a quick, private way to check their weight category. Fitness enthusiasts can track changes over time, individuals on weight management programs can monitor progress, healthcare workers can perform preliminary screenings, and students can learn about body composition metrics. Since all processing happens in your browser, your health data stays completely private.
Disclaimer
BMI is a screening tool and does not diagnose body fatness or health conditions. It does not account for muscle mass, bone density, or body composition. Consult a healthcare professional for a complete health assessment.
Last Reviewed and References
Last reviewed: July 2026. This page uses the standard adult BMI calculation and category ranges commonly published by public health organizations. For additional context, see the CDC adult BMI calculator guidance and the World Health Organization BMI topic page.
Practical Example
If an adult weighs 70 kg and is 1.75 m tall, BMI is calculated as 70 / 1.752 = 22.9. That falls inside the standard normal-weight range for adults. The category is a screening label, not a diagnosis.
Medical Disclaimer
BMI can be misleading for athletes, older adults, pregnant people, children, and people with medical conditions that affect fluid balance or body composition. Use the result as a general screening reference and speak with a qualified clinician for personalized health advice.