Free BMI Calculator Online
Calculate your Body Mass Index in metric or imperial units. Instantly see your BMI value and health category.
About the BMI Calculator
Body Mass Index (BMI) is a measure of body fat based on height and weight. It is calculated by dividing weight in kilograms by the square of height in metres (kg/m²). While BMI is a useful screening tool, it does not directly measure body fat percentage or account for muscle mass, bone density, or body composition.
The World Health Organisation (WHO) defines BMI categories as: Underweight (<18.5), Normal weight (18.5–24.9), Overweight (25–29.9) and Obese (≥30). This calculator supports both metric (kg/cm) and imperial (lbs/ft) inputs.
How to Calculate Your BMI
Choose Unit System
Select Metric (kg/cm) or Imperial (lbs/ft/in) depending on your preference.
Enter Weight & Height
Type in your weight and height in the fields provided.
Click Calculate BMI
Your BMI value, category and a visual scale bar appear instantly.
Frequently Asked Questions
A BMI between 18.5 and 24.9 is considered normal/healthy weight by the WHO. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
BMI does not distinguish between muscle and fat. Athletes or heavily muscular individuals may have a high BMI without being obese. Consult a healthcare professional for a complete assessment.
Yes — your height, weight and unit preference are saved in localStorage on your device and pre-filled on your next visit. Nothing is sent to any server.
Both metric (kilograms and centimetres) and imperial (pounds, feet and inches) are fully supported. Switch with the unit toggle buttons.