BMI Calculator — Body Mass Index with Interpretation
Calculate your BMI instantly. Get WHO category, healthy weight range, BMI Prime, and AI-powered health interpretation — free, fast, and accurate.
Enter your height and weight to calculate your Body Mass Index.
What is this calculator?
The BMI Calculator computes your Body Mass Index (BMI) using your height and weight. BMI is a simple measure that estimates body fat and helps categorize weight status according to World Health Organization (WHO) standards.
Formula
BMI is calculated as weight in kilograms divided by height in meters squared: BMI = weight_kg / (height_cm / 100)^2. For imperial units, BMI = (weight_lb / (height_in)^2) × 703. The calculator also computes BMI Prime (BMI/25) and Ponderal Index (weight_kg / (height_m)^3).
Example
For a person with height 170 cm and weight 70 kg: BMI = 70 / (1.70)^2 = 24.22 kg/m². This falls in the 'Normal weight' category (18.5–24.9). The healthy weight range for this height is 53.5–72.3 kg.
How to use
- 1Enter your height in centimeters (or feet/inches if using imperial) and your weight in kilograms (or pounds). Optionally, provide your age and sex for a body fat estimate.
- 2Click Calculate to compute your BMI, BMI Prime, Ponderal Index, and healthy weight range. If age and sex are provided, an estimated body fat percentage is also calculated using the Deurenberg formula.
- 3Your BMI value is compared to WHO categories: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), and Obese (≥30). BMI Prime shows how close you are to the upper normal limit (1.0 = BMI 25). The Ponderal Index adjusts for height differently.
Frequently Asked Questions
How is BMI calculated for children or teenagers?
What does BMI Prime mean?
Can BMI be inaccurate for athletes or muscular individuals?
How is the body fat estimate calculated?
What are the WHO BMI categories?
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