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 allows the calculator to instantly show the BMI value after the user clicks the calculate button.
Live Demo
You can try the working calculator here:
https://yuvronixstudio.github.io/simple-bmi-calculator/
UI Example
Source Code
GitHub:
https://github.com/YuvronixStudio/simple-bmi-calculator
Small Resource
I’ve also built a few other small JavaScript calculators, like an EMI calculator and an Interest calculator.
If you'd like the full source code bundle for these tools, you can find it here:
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