BMI Calculator
Calculate your Body Mass Index from height and weight, in metric or imperial, with your category and healthy weight range.
Your result
Where you fall on the BMI scale
About the BMI Calculator
This free BMI calculator works out your Body Mass Index from your height and weight in either metric (kg, cm) or imperial (lb, ft/in) units. As you type, it shows your BMI, the category it falls into — underweight, normal, overweight or obese — and the weight range that would put you in the healthy band for your height. Everything is calculated in your browser, so your details are never uploaded.
Body Mass Index is a quick, widely used screening number, but it has limits: it is based on height and weight alone, so it can read high for very muscular people and low for those who have lost muscle, and it is not meant for children, teenagers or during pregnancy. Use your result as general guidance to understand roughly where you stand — not as a medical diagnosis. For personal advice, talk to a healthcare professional.
Frequently asked questions
Answers to the questions we hear most about this tool.
What is BMI (Body Mass Index)?
Body Mass Index is a simple number that estimates whether your weight is in a healthy range for your height. It is calculated from your weight and height alone and is widely used as a quick screening tool by doctors and health organizations. A result between 18.5 and 24.9 is generally considered a healthy weight, below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above falls into the obesity range.
How do I calculate my BMI?
In metric units, BMI is your weight in kilograms divided by the square of your height in metres (kg/m²) — for example, 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. In imperial units, multiply your weight in pounds by 703 and divide by the square of your height in inches (703 × lb ÷ in²). This calculator does the maths for you in either unit and also shows your category and the weight range that would put you in the healthy band.
What is a healthy BMI range?
For most adults a BMI from 18.5 to 24.9 is classed as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 and above is obesity (sometimes split into class I 30–34.9, class II 35–39.9 and class III 40+). The same thresholds apply to men and women. This tool highlights your category on a colour-coded scale and tells you the weight range that corresponds to a healthy BMI for your height.
How accurate is BMI and what are its limits?
BMI is a useful, quick estimate but it is not a direct measure of body fat or health. Because it only uses height and weight, it can overestimate body fat in very muscular people (such as athletes) and underestimate it in older adults who have lost muscle. It is not designed for children and teenagers (who use age- and sex-specific percentiles) or for pregnant people. Treat your result as general information and a starting point for a conversation with a healthcare professional, not a diagnosis.
Is this BMI calculator free and private?
Yes. It is completely free with no sign-up, and every calculation runs entirely in your browser with JavaScript. Your height and weight are never sent to or stored on any server, so your information stays on your device and the calculator keeps working offline once the page has loaded.
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