BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight. Supports metric and imperial units with category results.
About This Free Online BMI Calculator
Our free online BMI calculator works out your Body Mass Index from your height and weight in seconds. Switch between metric (kilograms and centimeters) and imperial (pounds, feet, and inches) units, and the tool instantly shows your BMI value and the weight category it falls into — underweight, normal, overweight, or obese — based on standard World Health Organization ranges. BMI is a quick screening number, not a diagnosis. All calculations run in your browser, so your health data never leaves your device.
Features of Our BMI Calculator
- Calculate BMI in metric or imperial units
- Instant weight category (underweight, normal, overweight, obese)
- Color-coded result based on WHO ranges
- Feet-and-inches height entry for imperial
- Live results as you type
- 100% private — browser-only processing
How to Use the BMI Calculator
Using this tool is simple and requires no signup or registration. Follow these steps:
- Choose your unit system: Metric (kg/cm) or Imperial (lb/ft/in).
- Enter your weight and height in the fields shown.
- Read your BMI value and weight category instantly.
- Click Copy or Download to save your result.
Frequently Asked Questions About BMI Calculator
How is BMI calculated?
BMI equals your weight in kilograms divided by the square of your height in meters (kg/m²). In imperial units, BMI = 703 × pounds ÷ inches². This tool applies the correct formula automatically for the units you choose.
What is a healthy BMI range?
Standard categories are: under 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese. These ranges apply to most adults.
Is BMI accurate for everyone?
BMI is a useful screening tool but does not measure body fat directly. It can overestimate for very muscular people and underestimate for older adults with less muscle. Treat it as a general guide, not a medical diagnosis.
Does this work for children?
This calculator uses adult BMI categories. BMI for children and teens is interpreted differently using age- and sex-specific percentiles, so consult a pediatric BMI chart for under-20s.
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