A BMI (Body Mass Index) calculator web tool built using HTML, CSS, and JavaScript is a tool that allows users to calculate their body mass index (BMI) based on their height and weight. The web tool consists of a simple user interface that prompts the user to enter their height and weight, and then calculates their BMI using the standard formula (BMI = weight in kilograms / (height in meters)^2). The result is then displayed to the user, along with a message indicating whether their BMI falls within the underweight, healthy, overweight, or obese range. The tool is designed to be easy to use and accessible to anyone with an internet connection, providing a quick and convenient way to assess their health status.