Converting a forgotten free tool into $500 MRR after 3 months

Last year, I wrapped up another project that got zero traction.

And that led me to reflect on some emails I kept getting from Google Search Console:

"Congrats on reaching 9k clicks in 28 days!"
"...10k clicks"
"...11k clicks"

I'd built a free truss analysis tool four years ago while learning React, deployed it to GitHub Pages, and mostly forgot about it.

It also required an email submission for recurring users, so I decided to check how many contacts I had collected.

Over 20,000 unique email addresses in 2 years. And I'd never sent a single email to any of them.

Why was this tool growing all by itself

After building the tool out of personal need, I moved on to projects I thought would actually make money. None of them got any traction.

Meanwhile, this truss calculator I'd built in 2022 kept growing. Here's why I think it took off:

1. It solved a niche but surprisingly common problem.

Trusses are everywhere. Every triangular-roofed house, church, or warehouse probably has them. It sounded incredibly niche until I saw how many DIY homeowners, small contractors, and solo engineers need exactly this calculation.

2. The competition was terrible.

I literally built this because I googled "free truss analysis software" for a pro bono project in Mexico and hated everything I found. Just doing it by hand was unreasonably tedious.

3. I added transparency.

This was huge. My tool was unique in that it provided a detailed calculation report showing exactly how the result was reached. In a field where mistakes mean buildings fall down, transparency builds massive trust. Every other free tool was a black box.

4. Basic SEO actually mattered.

I picked the domain trussanalysis.com and put some effort into keywords. Most alternatives had weak SEO or lived on subdomains of university websites.

The email collection strategy for thousands of leads

A friend suggested I start collecting emails, but I was worried it would kill my traffic.

My solution: only ask after users were invested. After clicking "analyze" three times, I showed a simple form. You couldn't analyze more trusses until you submitted your email.

That's it. Still free, no password, just email.

I started this in March 2023. By October 2025, when I launched the paid version, I had 28,000 emails.

Building the paid version

After realizing I'd been sitting on actual distribution, I gathered user feedback from inbound emails over the years and built a paid MVP.

A few months of nights and weekends later, I had user accounts, payments, and highly requested features like multiple load cases and member design.

I launched a beta in October 2025 at 50% off ($10/month, $80/year, $180 lifetime).

The conversion strategy: I deployed to the same domain to preserve SEO strength, then added strategic upsell buttons at natural workflow points.

When someone went to add loads, they'd see "add multiple load cases with the pro version" right when they wanted it.

A controversial move nobody noticed

Here's where I broke a common rule: I moved a feature that used to be free behind the paywall.

Distributed load application became paid-only. I'd heard repeatedly that you shouldn't paywall previously free features because it upsets users.

But this intentional move strengthened the value proposition for customers who mattered.

And I got zero backlash. No one seemed to notice.

Why? The free app is largely B2C with high churn. Most people use it once and never return. New users don't know what used to be free.

The ones who do come back and need it? Exactly the power users willing to pay.

The numbers after 3 months

I removed the 50% discount in December, worried people would stop paying, but they didn't.

I got fewer new subscribers, but kept increasing revenue past $500 MRR thanks to the price increase.

Churn was high (42%), especially in the beginning. But after the price increase and releasing v1.0, it's down into the teens.

The conversion gap: 750 users created accounts but stopped at the paywall. That's a ton considering only ~80 users have paid for the app - it's one of my biggest opportunities. I think pricing isn't clear enough upfront.

The unused asset: Those 28,000 emails are now 32k untapped warm leads. Many are students (the free tool got linked by a popular STEM learning site), but plenty are business emails from engineers and contractors. I'm planning my first campaign soon.

I learned some obvious and non-obvious lessons

Distribution is everything for solo developers. I can build good solutions, but without access to high-intent buyers, I can't make money. The paid tool worked because it had organic distribution baked in. My failed projects severely lacked this.

People buy solutions to problems, not cool projects. The truss tool solved a specific problem people were actively searching for.

Trust matters in high-stakes domains. Detailed calculation reports weren't just nice - they built the trust that made people confident enough to pay.

Existing markets beat invented ones. Selling to people who already know they need truss analysis is infinitely easier than teaching engineers they need a new workflow tool (failed project number 2).

Some rules are meant to be broken. Paywalling free features and running high-churn B2C as a solo dev get hate. But rules of thumb are coarse with edge cases. I have high churn and low prices, but near-zero onboarding or support costs. It's a good starting point.

Segment early. My biggest mistake was not collecting more info during free tool email collection. High schoolers using it for class will never convert but they might be my largest segment. Knowing user intent from the start would allow me to target only the right potential customers.

What's next: leaving my comfort zone

Two weeks ago, a truss fabrication company emailed looking to replace their current design solution.

That sparked an idea.

There might be enterprise customers who'd find my core product useful with the right augmentations and positioning. But I'm not a user in that context, so I'll need to rely more on research and interviews to drive the roadmap.

I'm early in exploring this, staying flexible. The low-touch B2C model works, but I want a higher growth ceiling for full self-employment.

I'm also finally emailing those 32,000 people to see if I can win some conversions.

If you've navigated the transition from self-serve to enterprise, or have advice on this, I'd love to hear from you.

This is my first rodeo, and I'm learning as I go.