How to Calculate BMI Using JavaScript (Step-by-Step Guide)

When learning JavaScript, building small practical tools is one of the best ways to understand how programming logic works. A BMI (Body Mass Index) calculator is a perfect beginner project because it combines user input, mathematical calculations, and dynamic updates on the page. In this article, we'll break down how BMI is calculated and how to implement it using JavaScript. What is BMI? BMI stands for Body Mass Index. It is a simple calculation used to estimate whether a person has a healthy body weight relative to their height. The formula is: Where: Weight is measured in kilograms Height is measured in meters Example Calculation Let's say: The BMI calculation becomes: This value falls within the normal BMI range. BMI Categories Most BMI calculators classify results like this: You can use these ranges to show users what their BMI means. Implementing the Logic in JavaScript First, we collect user input. Next, we apply the BMI formula. Finally, we display the result. This simple logic