BMI Calculator
Calculate your Body Mass Index in metric or imperial units, compare it to the WHO category scale and see the healthy weight range for your height.
Updated September 2026 · Written and verified by Akash Pandey
BMI Calculator
How to use the BMI calculator
- Choose metric (kg/cm) or imperial (lb/in) units.
- Enter your height and weight.
- The BMI, WHO category and healthy weight range for your height are shown instantly.
Frequently asked questions
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². In imperial, the formula is weight (lb) × 703 ÷ height (in)² - the tool converts for you.
What are the BMI categories?
WHO categories: under 18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, 30+ obesity (with further sub-classes). This tool uses the same thresholds.
Is BMI accurate for athletes?
No - BMI cannot distinguish muscle from fat, so a muscular person can score "overweight" while being lean. It is a population statistic, best interpreted with body composition in mind.
What is a healthy BMI?
The 18.5-24.9 range. The tool also shows the healthy weight band for your exact height so you can see how far values sit from the boundary.
Does it follow the same rules for children?
No - children use age- and sex-adjusted percentile charts, which this adult-oriented calculator does not implement.
Is it private?
Yes - measurements are computed in your browser and nothing is stored or sent.
What is the formula for calculating BMI in metric and imperial?
Metric: weight (kg) / [height (m)]². Imperial: [weight (lbs) / height (in)²] × 703.
What are the standard World Health Organization (WHO) BMI categories?
Underweight is < 18.5, normal weight is 18.5–24.9, overweight is 25.0–29.9, and obesity is 30.0 or higher.