BMI Calculator
Check your Body Mass Index instantly in metric or imperial units.
Body Mass Index (BMI) is a quick screening measure that relates your weight to your height. It is used worldwide by health organizations to classify weight status in adults. Enter your height and weight above — in either metric (kg, cm) or imperial (lb, ft/in) units — and this calculator returns your BMI along with your World Health Organization category.
How this BMI calculator works
The calculator uses the standard formula: weight in kilograms divided by height in meters squared (imperial inputs are converted automatically). Results update instantly as you type — nothing is sent to a server, and none of your data is stored.
Understanding your result
A BMI between 18.5 and 24.9 is considered the healthy range for most adults. Below 18.5 is classed as underweight, 25–29.9 as overweight, and 30+ as obesity. Remember that BMI is a screening tool, not a diagnosis — it doesn't distinguish muscle from fat and doesn't account for age, sex or body composition. Read our full guide on what BMI really tells you for the details and limitations.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered the healthy range by the World Health Organization. Values below 18.5 indicate underweight, 25–29.9 overweight, and 30 or above obesity.
Is BMI accurate for athletes?
Not always. BMI cannot distinguish muscle from fat, so muscular people often score in the overweight range despite low body fat. Athletes should pair BMI with measures like waist circumference or body-fat percentage.
How is BMI calculated?
BMI equals your weight in kilograms divided by the square of your height in meters. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared.
Is my data stored when I use this calculator?
No. All calculations run entirely in your browser. Your height and weight are never sent to our server or stored anywhere.