BMI Calculator
Find your body mass index and healthy weight range in seconds — metric or imperial.
This BMI calculator works out your body mass index from your height and weight using the standard WHO formula, BMI = kilograms divided by metres squared. Switch between metric (cm, kg) and imperial (ft, in, lb), and it instantly shows your BMI to one decimal, your WHO weight category, and the healthy weight range for your height. Everything runs in your browser, so your numbers are never uploaded. BMI is a quick screening estimate that does not account for sex, muscle mass, or body composition, and it is not medical advice.
Frequently Asked Questions
How is BMI calculated?
BMI equals your weight in kilograms divided by the square of your height in metres (kg/m²). For imperial units this calculator first converts feet, inches, and pounds to metric, so the result is identical. It then rounds your BMI to one decimal place.
What are the BMI categories?
Using the World Health Organization ranges for adults: Underweight is below 18.5, Normal weight is 18.5 to 24.9, Overweight is 25 to 29.9, and Obese is 30 or above. This tool shows your category with a colour-coded badge.
What is a healthy weight for my height?
A healthy weight is the range that keeps your BMI between 18.5 and 24.9 for your height. The calculator computes this range for you and shows it in your chosen unit (kg or lb) so you have a concrete target.
Does BMI use age or sex?
No. The standard adult BMI formula uses only height and weight. Age and sex are optional here for context only — for example, BMI-for-age percentile charts are used for children and teens under 20, and older adults may sit slightly higher.
Is BMI accurate for athletes or muscular people?
BMI is a screening estimate, not a body-fat measurement. Very muscular people can have a high BMI with low body fat, and BMI does not capture fat distribution. Treat it as a starting point, not a diagnosis.
Should I use metric or imperial?
Either — use whichever you know. Toggle to Metric to enter centimetres and kilograms, or Imperial for feet, inches, and pounds. The BMI value is the same because the tool converts imperial to metric before calculating.
Is my data private?
Yes. The whole calculation happens in your browser with JavaScript. Nothing you type is sent to a server, stored, or shared, and there are no ads or signup.
Is BMI medical advice?
No. BMI is a general screening tool. For a full picture of your health, talk to a qualified healthcare professional who can also consider waist measurement, body composition, and your medical history.