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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Usage
- Quick personal screening at home before a clinic visit.
- See the healthy weight band for your height in metric or US units.
- Switch unit systems without retyping your measurements.
- Supplementary body-fat and waist-risk estimates for context.
- Educational comparison when setting realistic fitness goals.
Knowledge
Body Mass Index (BMI) is weight divided by height squared (kg/m² or lb/in² with the appropriate conversion). It classifies adults into broad bands such as underweight, normal, overweight, and obese.
Screening, not diagnosis. BMI does not distinguish muscle from fat and may misclassify athletes, older adults, and some ethnic groups. Optional body-fat (Deurenberg) and relative fat mass (RFM) estimates add context but are still approximations.
Healthy range. For most adults, a BMI between 18.5 and 24.9 is considered normal weight. Age 65+ may use adjusted bands in this tool. Always consult a healthcare professional for personal advice.
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.