BMI Calculator
Calculate your Body Mass Index and see your WHO adult weight category, in metric or imperial units.
| Underweight | Below 18.5 |
|---|---|
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
How to use this tool
Choose metric or imperial units, enter your weight and height, and select "Calculate BMI". Your BMI and weight category appear instantly.
About this calculation
BMI = weight (kg) / height (m)². The categories shown follow the World Health Organization's standard adult BMI classification. BMI is a simple screening tool, not a diagnostic measure — it doesn't account for muscle mass, bone density, body composition, sex, or age, and shouldn't replace an assessment by a healthcare professional.
Source: World Health Organization BMI classification for adults. This tool is for general informational purposes only and is not medical advice.
Frequently asked questions
How is BMI calculated?
BMI = weight in kilograms divided by height in meters squared (kg/m²). For imperial units, BMI = 703 × weight in pounds / (height in inches)².
What are the WHO BMI categories for adults?
Below 18.5: underweight. 18.5–24.9: normal weight. 25–29.9: overweight. 30 and above: obese (often further split into class I 30–34.9, class II 35–39.9, and class III 40+).
Is BMI accurate for everyone?
No. BMI doesn't distinguish muscle from fat, so it can overestimate body fat in muscular or athletic people and underestimate it in older adults who've lost muscle mass. It's a population-level screening tool, not a diagnosis, and doesn't apply the same way to children, pregnant women, or the very elderly.
Should I use BMI alone to judge my health?
No. BMI is one screening indicator among many. Waist circumference, body composition, blood pressure, and other health markers matter too. For a full health assessment, consult a doctor or qualified health professional.