BMI Calculator
Body Mass Index · all ages · precise metrics · healthy weight targets · BMI Prime & Ponderal Index
— kg/m²
—
BMI Prime: — (—%)
Ponderal Index: — kg/m³
Healthy BMI range (adults): 18.5 – 24.9 kg/m²
Healthy weight for height: —
⚖️ Weight to lose/gain to BMI 24.9: —
📉 To BMI 18.5: —
📊 WHO BMI Classification (adult reference)
| Category | BMI (kg/m²) |
|---|---|
| Underweight (severe thinness) | < 16.0 |
| Underweight (moderate) | 16.0 – 16.9 |
| Underweight (mild) | 17.0 – 18.4 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity class I | 30.0 – 34.9 |
| Obesity class II | 35.0 – 39.9 |
| Obesity class III | ≥ 40 |
🧒 For all ages: BMI calculation is the same formula. However, for children and teens (ages 2–20), BMI is interpreted using age- and sex-specific percentiles. This tool provides raw BMI and healthy weight targets based on adult ranges. Please consult a pediatrician or growth charts for children.
📐 Additional metrics
BMI Prime = BMI / 25 → percentage of upper healthy limit.
Ponderal Index (PI) = weight(kg) / height(m)³, helpful for stature extremes.
✓ Done
BMI Calculator
Key facts about Body Mass Index (BMI):
- Basic Definition
BMI is a number calculated from a person’s weight and height:
BMI=weight (kg)/height (m)2 - Standard Categories (for adults)
- Underweight: < 18.5
- Normal weight: 18.5–24.9
- Overweight: 25–29.9
- Obesity: ≥ 30 (further divided into Class I, II, III)
- Does Not Measure Body Fat Directly
BMI is a surrogate marker, not a direct measurement of body fat percentage or distribution. - Same for Both Sexes, but Differences Exist
The same BMI range is used for men and women, but women naturally carry more body fat than men at the same BMI. - Not Accurate for Everyone
BMI can misclassify:- Athletes (high muscle mass may show as overweight/obese)
- Older adults (muscle loss may hide excess fat)
- Pregnant or breastfeeding women
- Certain ethnic groups (e.g., Asians have higher health risks at lower BMI)
- Health Risk Predictor
Higher BMI (especially ≥ 30) is linked to increased risk of:- Type 2 diabetes
- Heart disease
- Hypertension
- Certain cancers
- Sleep apnea
- Limitation: Doesn’t Show Fat Location
Waist circumference is often better at predicting visceral fat (fat around organs), which carries higher metabolic risk.