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.
Worked example: Indian-specific cut-offs
The Indian Council of Medical Research (ICMR) recommends slightly tighter BMI cut-offs for Indians, since cardiometabolic risk in South Asians often appears at lower BMI than in Caucasian populations. The numbers below show the same person scored against both standards.
- Sample weight
- 72 kg
- Sample height
- 170 cm
- BMI
- 24.9 kg/m²
- WHO classification
- Normal (18.5–24.9)
- ICMR / Indian classification
- Overweight (23–24.9)
Indian cut-offs (Misra et al., consensus 2009): <18 underweight, 18–22.9 normal, 23–24.9 overweight, ≥25 obese. WHO international cut-offs: <18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, ≥30 obese. South Asian bodies tend to carry more visceral fat at the same BMI, which is why Indian guidelines are tighter.
Two limitations to remember. BMI does not distinguish muscle from fat — well-trained athletes routinely show as "overweight". And waist-to-hip ratio (above 0.90 for men, 0.85 for women per WHO) often flags metabolic risk earlier than BMI.
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.