BMI Calculator — Free Online Body Mass Index Calculator
Calculate your Body Mass Index (BMI) and see which category you fall into. Supports metric and imperial units. All calculations happen locally — nothing leaves your browser.
How to Use the BMI Calculator
- Choose units — select metric (kg/cm) or imperial (lbs/ft+in).
- Enter height — your current height in the selected units.
- Enter weight — your current weight in the selected units.
- View results — see your BMI, category, and ideal weight range.
Understanding BMI
Body Mass Index (BMI) is a simple calculation using height and weight. It's a useful screening tool, but doesn't account for muscle mass, bone density, or body composition. Athletes may have a high BMI due to muscle weight while being perfectly healthy.
Categories: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese (≥30). BMI Prime (your BMI divided by 25) gives a quick ratio — below 1 is healthy, above 1 indicates overweight.
Frequently Asked Questions
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so athletes may register as overweight. It's also less accurate for elderly people, pregnant women, and very muscular individuals. Use it as one data point, not the whole picture.
The WHO defines a healthy BMI as 18.5-24.9. However, some research suggests 20-25 may be optimal for longevity. BMI Prime (BMI/25) below 1.0 is considered healthy.
BMI is reduced by losing weight relative to height. Focus on sustainable changes: balanced nutrition, regular physical activity, adequate sleep, and stress management. Consult a healthcare provider for personalized advice.
Use Cases
Fitness Progress Tracking
Monitor your BMI changes over time to track fitness progress and measure the effectiveness of your workout routines.
Pre-Checkup Screening
Calculate your BMI before a medical checkup to have informed discussions with your healthcare provider about your weight.
Weight Management Goals
Set realistic weight management goals by understanding your current BMI category and ideal weight range.
Metric vs Imperial BMI
Compare BMI calculations between metric and imperial units to verify accuracy across different measurement systems.
Wellness Program Assessments
Use BMI calculations for corporate wellness program assessments and employee health screening initiatives.