What I Learned Building a Free Online Calculator Site (The Hard Way)

Isfahan Ali — Thu, 07 May 2026 21:23:06 +0000

I launched MyCalculator.us thinking it would be a small weekend project.
Build a few tools.
Put them online.
Maybe get some traffic.
Six months later, I've learned more about what people actually need from the web than I ever expected.
Here's what surprised me.

People Search With Very Specific Intent
I assumed visitors would land on a homepage and browse.
They don't.
They type exactly what they need into Google.
"How much mortgage can I afford on a 60k salary"
"BMI calculator metric"
"crypto tax calculator US"
Each one of those is a different person with a different problem who needs a specific answer right now.
So I stopped thinking about my site as a product.
I started thinking of each calculator as its own standalone answer to a real question.
That changed everything about how I built pages.

The Tool Is Just the Beginning
My first version of the mortgage calculator was just fields and a result.
Input home price.
Input down payment.
Get monthly payment.
Done.
Except — users were confused.
They didn't know what interest rate to enter.
They didn't understand what PMI was.
They didn't know if their result was good or bad.
The calculator was technically correct.
But it wasn't useful.
I rewrote every page with context:
What this number means.
What affects it.
What you should do with it.
Usefulness isn't just accuracy.
It's clarity.

Simple Calculators Get More Traffic Than Complex Ones
I spent two weeks building an advanced investment model with 14 variables.
It got almost no traffic.
Meanwhile, the BMI calculator — which took me a few hours — drives consistent traffic every week.
Why?
Because BMI is what people search for.
People type "BMI calculator" into Google every day.
Nobody searches for "advanced multi-variable investment projection tool."
I learned to start with demand, not ideas.
Build what people are already looking for.
Then make it the best version of that thing on the internet.

Mobile Is Where Most Users Actually Are
I built everything on a laptop.
Tested on a laptop.
Assumed most users were on laptops.
Wrong.
When I looked at the analytics, over 65% of users were on mobile.
My loan calculator had input fields that were too small to tap.
The result text was tiny.
The layout broke on narrow screens.
I spent a whole week just fixing mobile issues I should have caught on day one.
Now I test on mobile first. Always.
If it doesn't work on a phone, it doesn't ship.

Salary Questions Are Surprisingly Common
I almost didn't build a salary calculator.
It felt too simple.
Then I looked at the search volume.
Huge.
People constantly want to know:
"How much is $25/hour annually?"
"What's my hourly rate if I earn $55k a year?"
The salary to hourly calculator became one of the most visited pages on the site.
Simple problems.
Massive search demand.
Never underestimate simple.

Niche Calculators Can Win Surprisingly Fast
When I added a crypto tax calculator, I expected it to take months to rank.
It didn't.
Because most calculator sites weren't covering that space yet.
The lesson: go where your competitors haven't bothered to go.
There are whole categories of questions people search for every day that nobody has built a good tool for.
Find the gaps.
Fill them properly.

What I'd Do Differently From Day One
Start mobile-first.
Build for search intent, not personal interest.
Write enough context that the tool actually teaches the user something.
Don't ignore niche topics — that's where you can rank fast.
Keep URLs clean and descriptive.
Add internal links so calculators support each other.

Final Thought
Calculator sites work because people always need to calculate things.
That's not going away.
But the sites that win aren't just technically correct.
They're genuinely useful, clearly explained, and built for how real people actually search and browse.
That's the whole game.
And honestly, it's a pretty good game to be in.

If you're curious, the full collection of tools is at mycalculator.us — everything from mortgage to crypto to BMI, all free.

calculator #webdev #javascript #seo

DEV Community: Isfahan Ali

What I Learned Building a Free Online Calculator Site (The Hard Way)

calculator #webdev #javascript #seo