BMI Calculator
Free BMI calculator. Calculate your Body Mass Index in metric (kg/cm) or imperial (lbs/inches). Includes BMI category and healthy weight range.
BMI Calculator
Comprehensive Guide & Practice
Master the mathematical principles, formulas, and step-by-step methods with worked examples and FAQs.
1. What Is BMI?
Body Mass Index (BMI) is a numerical value calculated from a person's height and weight. It is widely used as a screening tool to categorise adults as underweight, normal weight, overweight, or obese.
Metric Formula: BMI = weight (kg) ÷ height² (m²)
Imperial Formula: BMI = 703 × weight (lbs) ÷ height² (inches²)
2. BMI Categories (WHO)
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5–24.9
- Overweight: BMI 25–29.9
- Obese Class I: BMI 30–34.9
- Obese Class II: BMI 35–39.9
- Obese Class III: BMI ≥ 40
Important: BMI is a screening tool, not a diagnostic tool. It does not account for muscle mass, bone density, age, sex, or ethnicity. Always consult a healthcare professional for health assessments.
See also: Age Calculator | Percentage Calculator