How to Use This Calculator
- Select your unit system: Toggle between Metric (centimeters/kilograms) or Imperial (feet/inches/pounds).
- Enter your height and weight: Provide your accurate current physical measurements.
- Review your category: Check your classification on the standard WHO scale.
Formula and Calculation Steps
Metric Formula: BMI = weight (kg) ÷ [height (m)]²
Imperial Formula: BMI = 703 × weight (lbs) ÷ [height (in)]²Worked Examples and Reference Table
| BMI Range | WHO Category | Health Risk Profile |
|---|---|---|
| < 18.5 | Underweight | Nutritional deficiency risk |
| 18.5 – 24.9 | Normal weight | Lowest mortality risk |
| 25.0 – 29.9 | Overweight | Moderate risk |
| 30.0 – 34.9 | Obesity Class I | High risk |
| 35.0 – 39.9 | Obesity Class II | Very high risk |
| ≥ 40.0 | Obesity Class III | Extremely high risk |
Frequently Asked Questions
What is a normal BMI for adults?
According to the World Health Organization (WHO), a normal BMI for adults aged 20 and over is between 18.5 and 24.9.
How accurate is BMI as a health metric?
BMI is an effective population screening tool, but it does not differentiate between fat mass and muscle mass. Athletes and bodybuilders may register as overweight due to dense muscle tissue.
What is the formula for calculating BMI?
In metric units: BMI = weight (kg) / [height (m)]². In imperial units: BMI = 703 * weight (lbs) / [height (in)]².
Does age or gender affect BMI classification?
For adults 20 and older, standard WHO BMI categories are identical for men and women regardless of age. For children and teens, BMI percentiles based on age and sex charts are used instead.
How can I calculate my healthy weight range?
Multiply 18.5 and 24.9 by the square of your height in meters. For someone 1.75m tall, the healthy weight range is roughly 56.7 kg to 76.3 kg (125 to 168 lbs).