BMI Calculator
Body Mass Index from height and weight. For wellness context only—not medical advice.
Calculate adult BMI from kilograms and centimetres, read off WHO-style categories, and use the spectrum bar as orientation only—athletes and clinical decisions still need waist measures or a doctor's judgement.
Measurements
Metric units.
Result
BMI = weight / height² (height in metres).
Where this BMI sits (adult scale)
Bands are approximate; clinical thresholds can vary by guideline.
Body Mass Index formula
BMI is weight divided by the square of height in metres. It correlates with body fat at a population level but not perfectly for every individual.
Metric BMI
BMI = mass_kg / (height_m)² height_m = height_cm / 100
- mass_kg
- Body mass in kilograms.
- height_m
- Stature in metres.
Categories shown (underweight, normal, overweight, obese) follow common WHO adult cut-offs used for quick self-assessment—not a substitute for clinical assessment.
Band reference (adults, illustrative)
These ranges are educational; individual risk also depends on waist size, blood pressure, glucose, lipids, and family history.
- Underweight — 10.0%
- Normal — 45.0%
- Overweight — 30.0%
- Obese — 15.0%
Proportions are not prevalence data—only a visual mnemonic.
Key terms
- BMI
- Single number summarizing weight-for-height; cheap to measure, easy to explain.
- Metabolic health
- How well your body handles energy—BMI is one input among many biomarkers.
- Visceral fat
- Fat around organs—linked to cardiometabolic risk even at “normal” BMI.
Benefits
- Quick self-check alongside other wellness metrics.
- Track changes if you are adjusting diet or activity under professional guidance.
- Private—no data leaves your browser on this site.
FAQ
Is BMI accurate for athletes?▼
BMI can misclassify very muscular people as overweight because it does not distinguish muscle from fat. Waist circumference, body composition scans, and clinical advice add context.
Why metric units?▼
The standard formula uses kilograms and metres. We accept height in centimetres and convert internally for convenience.
Are the categories medical advice?▼
No. WHO-style banding is a population screening tool. Only a qualified clinician should diagnose or treat health conditions.
What about children and teens?▼
BMI interpretation for minors uses age- and sex-specific growth charts—not implemented here.