Free Tool
BMI Calculator | Free Body Mass Index Calculator
Calculate your Body Mass Index (BMI) based on height and weight. Instant results with WHO classification categories.
Built by an engineer who chases finish lines and is obsessed with data. Thomas Prommer — technology executive who has worked with Google, Apple, Nike, Adidas, Netflix and other global brands. Also an Ironman finisher, HYROX Pro Division competitor, and marathon runner. These tools combine engineering rigor with real race experience.
BMI Calculator
Calculate your Body Mass Index based on height and weight. Instantly see your WHO classification.
How BMI is Calculated
BMI = weight (kg) / height (m)². Developed by Adolphe Quetelet in 1832, BMI is widely used by the World Health Organization as a screening tool. While useful for population-level assessments, BMI does not distinguish between muscle and fat mass, which can misclassify muscular athletes.
FAQ
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered normal weight by the WHO. However, BMI is just one metric — body composition, fitness level, and overall health matter more than the number alone.
Is BMI accurate for athletes?
BMI can be misleading for athletes because it does not distinguish muscle from fat. A muscular person may be classified as "overweight" despite having low body fat. FFMI is often a better metric for athletes.
How is BMI calculated?
BMI = weight in kilograms divided by height in meters squared. For example, a 70 kg person who is 1.75 m tall has a BMI of 70 / (1.75²) = 22.9.
What are the BMI categories?
WHO categories: Underweight (< 18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese Class I (30–34.9), Obese Class II (35–39.9), Obese Class III (40+).