I Built a Simple BMI Calculator Using Vanilla JavaScript

I needed a lightweight BMI calculator for a small project,
So I decided to build one using plain HTML, CSS, and vanilla JavaScript.

No frameworks. No libraries.
Just the basics.

Features

• Mobile responsive
• Instant BMI calculation
• Clean, minimal UI
• No external dependencies

Why I built it

Most BMI calculators online are cluttered with ads or unnecessary features.

I wanted something:

• Fast
• Simple
• Easy to reuse in other projects

Implementation overview

• HTML for structure and inputs
• CSS for layout and responsiveness
• JavaScript for:
  • Input validation
  • BMI calculation
  • Dynamic result updates

Demo & source

Live demo: (https://yuvronixstudio.github.io/simple-bmi-calculator/)

Source code: (https://yuvronixstudio.github.io/simple-bmi-calculator/)

What I learned

• For small tools, vanilla JS is often enough
• UI clarity matters more than complex logic
• Default values improve usability

I’m building more small, practical web tools like this
and sharing what I learn along the way.

Feedback on the UI or logic is welcome.