BMI Calculator Free Online
Calculate Body Mass Index (BMI) and see your WHO classification. Supports metric (cm, kg) and imperial (in, lb) units.
Results
Pro — bulk batch calculation, API access, history & favorites
API access · Priority queue · Team workspace
Related Tools
BMI Calculator Features
WHO Categories
7 categories from severely underweight (<16) through obese class III (≥40), matching World Health Organization classifications.
Metric & Imperial
Metric: kg ÷ m². Imperial: (lb ÷ in²) × 703. Same formula, this calculator handles unit conversion automatically.
Healthy Range
Shows the weight range (BMI 18.5-24.9) for your current height, plus how many kg/lb you are from the closest healthy threshold.
Live Calculation
Switch units or change values, all results recalculate.
Limitations
BMI does not account for muscle mass, bone density, or body composition. Athletes often score "overweight" despite low body fat.
100% Private
All math runs in your browser. No data leaves your device.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Full bmi calculation | ||
| Live calculation | ||
| All-units result panel | ||
| Bulk batch calculation | — | |
| REST API access | — | |
| Save & share calculations | — |
Frequently Asked Questions
BMI = weight (kg) ÷ height (m)². Or in imperial: (weight (lb) ÷ height (in)²) × 703. Both yield the same number.
WHO defines 18.5-24.9 as healthy weight for adults. Below 18.5 is underweight; 25-29.9 overweight; 30+ obese. These are population averages, not individual targets.
No — muscular athletes often have BMI >25 despite low body fat. BMI cannot distinguish muscle from fat. For body composition, use DEXA, calipers, or BIA scales.
Not directly — children use BMI percentiles by age and sex (BMI-for-age). Adult BMI categories apply from age 20+.
Many doctors recommend pairing BMI with waist measurement. Waist >40 in (102 cm) for men or >35 in (88 cm) for women indicates higher health risk regardless of BMI.