That Time I Wrote My Own Hex Tool… Then Found a Better One

So I was working on a small side project — just a fun little retro-style memory game in JavaScript — and I needed to deal with a bunch of hexadecimal values.

At first, I was doing quick conversions using parseInt() and .toString(16) in the console, but it quickly got annoying. I thought: “Hey, why not build my own hex converter in HTML + JS?”

I ended up making a tiny tool that:

Took decimal input and converted it to hex

Did basic addition/subtraction between two hex values

It was a cool learning experience (and I still recommend doing it if you're new to JS), but I quickly realized how many edge cases I hadn’t accounted for:

Validating hex inputs (especially lowercase vs uppercase)

Handling negative numbers in hex

Supporting multiple operations (add, subtract, multiply, divide)

Keeping the interface simple and readable

After hitting a few walls, I figured: “Let me see what tools are out there.”

And I stumbled across 👉 hexcalculator.org

It’s clean, fast, does exactly what I was trying to build — and more.
You can:

Convert between hex and decimal

Perform hex-based math operations

See live results without reloading the page

AND it doesn’t throw ads in your face (bless)

If you're ever working on low-level stuff, embedded code, color codes in CSS, or anything where you need to juggle hex values — this tool honestly saved me hours.

Not trying to plug anything — just sharing because I genuinely wish I'd found it sooner. 😅

Also: if you’re a beginner and want a real-world JS practice project, making your own basic hex converter is a fun challenge. But when you're ready to compare or go deeper, this site’s a solid reference.

Would love to hear — has anyone else tried building one of these from scratch? What did you struggle with?