What is BMI?
Body Mass Index (BMI) is weight divided by height squared. It gives a simple number used to classify underweight, healthy weight, overweight, or obesity for adults.
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FAQs
Which units can I use?
Choose Metric (kilograms and centimetres) or US units (pounds, feet, and inches). When you switch systems, measurements you have entered are converted so you do not lose your values.
Why ask for age, biological sex, and waist?
Age (65+) switches BMI category and healthy-weight bands to common older-adult screening ranges. With sex and age, the tool estimates body fat using the Deurenberg formula; with sex and waist, it uses relative fat mass (RFM). Waist is also checked against sex-specific risk thresholds. All are screening aids, not a diagnosis.
What do the BMI categories mean?
The tool shows a general WHO-style category (for example underweight, normal, overweight, or obese). These are population guidelines, not a personal diagnosis.
What is the healthy weight range?
For your entered height, the result includes the weight range that corresponds to a BMI between 18.5 and 24.9 in the units you selected.
Is this medical advice?
No. BMI is a screening tool only. Athletes, older adults, and other groups may need professional guidance beyond a simple BMI reading.
Is my data stored or sent to a server?
No. Height and weight are processed in your browser only. Nothing is uploaded or saved on a server.