How the bmi calculator works
BMI Calculator computes Body Mass Index, a widely used statistical screening benchmark created by Adolphe Quetelet to categorize adult body weight relative to height. The World Health Organization (WHO) and CDC classify BMI into four primary categories: Underweight (BMI < 18.5), Normal weight (18.5 – 24.9), Overweight (25.0 – 29.9), and Obesity (BMI ≥ 30.0).
While BMI serves as a convenient population screening metric, it does not distinguish between lean muscle mass and fat tissue. Consult healthcare professionals for personalized body composition assessments.
Step-by-step instructions
- Select your preferred measurement units: Metric (kg and cm) or Imperial (lbs and inches/feet).
- Enter your current weight and height.
- Click Calculate BMI to view your index score, WHO category classification, and reference ranges.
Standard BMI Formula
• Metric: BMI = Weight (kg) / [Height (m)]²
• Imperial: BMI = 703 × Weight (lbs) / [Height (inches)]²Weight is divided by the square of height in meters. In imperial units, a conversion scaling factor of 703 is applied to normalize pounds and inches to metric equivalents.
Practical example
A person who weighs 70 kg and is 175 cm tall (1.75 m): BMI = 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.86 (classified as Normal weight).
Frequently asked questions
Is BMI an accurate measure for athletes and bodybuilders?
No. BMI does not measure body fat directly. Athletes with high muscle mass may register as 'overweight' or 'obese' despite low body fat percentage.
Does this BMI calculation apply to children and teens?
This calculator uses adult BMI classifications (ages 20+). For children and teens, doctors use age-and-sex-specific BMI percentiles.
Is my personal health data recorded or sent anywhere?
No. All values are calculated entirely in your local browser window. No health or body metric is ever saved or transmitted.