maratoolBMI Calculator
Calculate Body Mass Index (BMI), classification, and body surface area from weight and height. Uses the WHO BMI categories and the Mosteller BSA formula.
For educational and clinical reference. Not a substitute for medical judgment.
BMI
—
Classification
—
Body Surface Area (Mosteller)
—
WHO BMI classification reference
| Category | BMI (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| 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 | ≥ 40.0 |
How to use
- Enter weight in kilograms and height in centimeters (or meters).
- BMI, classification, and body surface area update as you type.
- Use the copy button to copy any result to your clipboard.
Frequently asked questions
How is BMI calculated?
BMI = weight (kg) / height² (m²). For example, 70 kg at 1.75 m → 70 / (1.75 × 1.75) = 22.9 kg/m².
What are the WHO BMI categories?
Underweight: < 18.5 • 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.
What is body surface area (BSA) used for?
BSA is commonly used for chemotherapy dosing, cardiac index, and other body-size-adjusted calculations. This tool uses the Mosteller formula: BSA = √((Hcm × Wkg) / 3600).
Is this a substitute for medical evaluation?
No. This calculator is for educational use and does not replace clinical judgment. Always consult a healthcare professional for medical decisions.
Last updated
Powered by maratool