BMI Calculator
Calculate your Body Mass Index from your height and weight in metric or imperial units. See your WHO weight category and the healthy weight range for your height. Everything runs in your browser — your data is never sent anywhere and nothing is stored.
How to use the BMI calculator
- Choose Metric (cm, kg) or Imperial (feet + inches, lb).
- Enter your height and weight — the result updates as you type.
- Read your BMI number, the WHO category badge, and the healthy weight range for your height.
BMI is calculated as weight (kg) / height (m)². WHO categories: Underweight below
18.5, Normal 18.5–24.9, Overweight 25–29.9, Obese 30 or above. BMI is a screening tool, not a
diagnosis — speak to a doctor for a full assessment.
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Frequently asked questions
What is BMI?
BMI (Body Mass Index) is a number calculated from your height and weight: BMI = weight (kg) / height (m)². It gives a quick, single-number estimate of whether your weight is in a healthy range for your height, and is widely used for screening at a population level.
How is BMI calculated from imperial units?
Your feet and inches are converted to metres and your pounds to kilograms, then the standard kg / m² formula is applied. One inch is 0.0254 m and one pound is 0.45359237 kg, so the result matches the metric calculation exactly.
What are the BMI categories?
The World Health Organization (WHO) uses: Underweight below 18.5, Normal 18.5–24.9, Overweight 25–29.9, and Obese 30 or above. These thresholds apply to adults.
What is a healthy weight range for my height?
The calculator shows the weight range that corresponds to a BMI of 18.5 to 24.9 for your height. Staying within that range generally keeps your BMI in the Normal band.
Is my data sent anywhere?
No. The calculation runs entirely in your browser — your height and weight are never uploaded to a server and nothing is stored.
Are there limits to what BMI tells me?
Yes. BMI does not distinguish muscle from fat, so very muscular people can score high while still being healthy, and it may under-estimate body fat in older adults. It is a screening tool, not a diagnosis — talk to a doctor for a full assessment.