About the BMI Calculator
Body Mass Index (BMI) is a quick screening measure that compares your weight with your height. Move the sliders or type your height and weight to see your BMI instantly on a colour-coded scale, along with your weight category and the healthy weight range for your height.
BMI is a useful starting point but does not measure body fat directly and does not account for muscle mass, age, sex or ethnicity. Results are estimates for general information and are not a substitute for advice from a doctor or other qualified health professional.
How to use the BMI Calculator
- Choose metric (cm, kg) or imperial (ft/in, lb) units.
- Enter or slide to your height and weight.
- Read your BMI, your category and your healthy weight range.
Frequently asked questions
What is a healthy BMI?
For most adults the World Health Organization classes a BMI of 18.5–24.9 as healthy, 25–29.9 as overweight and 30 or more as obese. Below 18.5 is underweight.
How is BMI calculated?
BMI = weight in kilograms ÷ (height in metres)². For example, 70 kg and 1.75 m gives 70 ÷ 3.0625 ≈ 22.9.
Is BMI accurate for athletes?
Not always. Muscle is denser than fat, so muscular people can have a high BMI while having little body fat. A body fat measurement gives a better picture.
Is BMI the same for children?
No. Children and teenagers use BMI-for-age percentiles, because healthy body fat changes as they grow. This calculator is designed for adults aged 18 and over.