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BMI is a widely used screening tool but has important limitations. Understanding the categories — and when BMI misleads — helps you use it intelligently.
The Formula
BMI = Weight (kg) ÷ Height² (m²) | <18.5 underweight | 18.5-24.9 normal | 25-29.9 overweight | 30+ obese
Standard formula used by professionals worldwide
Worked Example
Step-by-step
Height 1.75m, weight 80kg → BMI = 26.1 → Overweight category
Key Concepts
- Accuracy: Results are as accurate as the inputs you provide
- Units: Always use consistent units throughout your calculation
- Verification: Double-check important calculations before making decisions
- Professional advice: For major financial, health, or structural decisions, consult a qualified professional
Privacy and Security
- All calculations run entirely in your browser
- No data is sent to any server
- No sign-up or personal information required
- Your data stays private — always
Frequently Asked Questions
BMI accurate for everyone?
No — overestimates fat in muscular people and underestimates in low muscle mass individuals.
BMI for Asian populations?
Health risks start at lower thresholds, around 23+ rather than 25+.
BMI high — what to do?
Consult a doctor. BMI is a screening tool, not a diagnosis.