Free BMI Calculator
Check your body mass index in seconds. Switch between imperial and metric units — your result and category appear instantly.
How to use the BMI calculator
- Choose imperial (feet/inches, pounds) or metric (centimeters, kilograms).
- Enter your height and weight.
- Your BMI and its category appear instantly below the form.
What BMI does and does not tell you
BMI is a quick screening number: your weight in kilograms divided by your height in meters squared. It is useful for spotting broad trends across populations, but it is a blunt instrument for individuals — it cannot distinguish muscle from fat, so athletes and very muscular people often land in the "overweight" range despite being perfectly healthy. It also does not account for age, sex, or where fat is carried, all of which matter for health. Treat your result as one data point, not a diagnosis: if your BMI is outside the healthy range and you are concerned, a doctor can look at the fuller picture with measurements like waist circumference, body fat percentage, and blood work. This calculator is for information only and is not medical advice.
Frequently asked questions
What is a healthy BMI?
The standard categories are: under 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, and 30 or above obesity. These are screening ranges, not diagnoses.
Is BMI accurate for muscular people?
Not really. BMI cannot tell muscle from fat, so people with a lot of muscle mass can score as "overweight" while being very fit. Athletes should use body-fat measurements instead.
Is my health data stored anywhere?
No. The calculation runs entirely in your browser. Your height and weight never leave your device.
Can children use this calculator?
Children's BMI is interpreted differently — against age-and-sex percentiles, not adult cutoffs. This tool uses adult categories, so it is not appropriate for children. Ask a pediatrician for guidance.