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Health & Fitness
BMI Calculator
Body Mass Index with the WHO categories. Results update as you type.
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Your BMI (kg/m²)
Enter height and weight
- Underweight< 18.5
- Normal18.5 – 24.9
- Overweight25 – 29.9
- Obese≥ 30
BMI is a screening estimate and does not account for muscle mass, age or body composition. It is not medical advice.
Body Mass Index (BMI) & Clinical Health Guidelines
Body Mass Index (BMI), pioneered by Belgian polymath Adolphe Quetelet, is an internationally standardized biometric screening tool. Adopted universally by the WHO and CDC, it classifies adult weight categories to evaluate population-level epidemiological risks of cardiovascular disease, type-2 diabetes, hypertension, and osteoarthritis.
Metric Formula:
Imperial Formula:
WHO Categories: <18.5 Underweight • 18.5–24.9 Normal • 25–29.9 Overweight • ≥30 Obese
BMI = Weight (kg) / [Height (m)]²Imperial Formula:
BMI = 703 × Weight (lbs) / [Height (inches)]²WHO Categories: <18.5 Underweight • 18.5–24.9 Normal • 25–29.9 Overweight • ≥30 Obese
Realistic Worked Example: Adult Biometric Assessment
Input: Height = 175 cm (1.75 meters) • Weight = 70.0 kg (154.3 lbs).
1. Compute Height Squared: 1.75 × 1.75 = 3.0625 m².
2. Divide Mass by Height Squared: 70.0 ÷ 3.0625 = 22.857 kg/m².
3. Derive Healthy Weight Envelope (18.5 to 24.9):
• Minimum: 18.5 × 3.0625 = 56.66 kg.
• Maximum: 24.9 × 3.0625 = 76.26 kg.
Result: 22.9 kg/m² • Status: Normal Weight (Target healthy range: 56.7 kg – 76.3 kg).
1. Compute Height Squared: 1.75 × 1.75 = 3.0625 m².
2. Divide Mass by Height Squared: 70.0 ÷ 3.0625 = 22.857 kg/m².
3. Derive Healthy Weight Envelope (18.5 to 24.9):
• Minimum: 18.5 × 3.0625 = 56.66 kg.
• Maximum: 24.9 × 3.0625 = 76.26 kg.
Result: 22.9 kg/m² • Status: Normal Weight (Target healthy range: 56.7 kg – 76.3 kg).
Clinical Nuances & Limitations
- Muscle vs. Adipose Tissue: BMI measures weight density, not body fat percentage. Muscular athletes often score in the "overweight" range despite having healthy <12% body fat.
- Age Considerations: For older adults (>65 years), clinical research suggests a slightly higher BMI (23–27 kg/m²) is protective against osteoporosis and frailty.
- Pediatric Caution: Adult BMI cutoffs do not apply to children or teenagers; pediatric growth percentiles (CDC/WHO) must be referenced.