The story behind this site
This project started in 2024 as a personal weekend tool. I was helping my sister figure out the real discount on a stacked Black Friday deal — "30% off, then an extra 20% at checkout" — and was annoyed that every percentage calculator I opened on Google buried a one-line answer under a five-megabyte page, three popups and a cookie banner that hijacked the back button. I wrote a 200-line HTML file, sent it to her, and forgot about it.
Six months later that page had quietly picked up traffic. Friends were forwarding it. A teacher in Brazil emailed asking if they could use it in class. By the time we hit a few thousand monthly users I'd added a tip splitter, a discount calculator, a compound-interest tool and a fraction converter — and the whole thing was still a single HTML file with no tracking.
The current version is the result of about eighteen months of evenings: a proper PWA, a Chrome extension, 15 interactive lessons, an interactive quiz, finance calculators with amortization charts, a bulk-CSV mode, and translations into twelve languages contributed by math educators we found through forums and friends-of-friends. None of those people are paid — they did it because the same tool helps them teach their own students.
We're not a company. There's no funding round, no growth target, no "user acquisition" team. The site is funded by a single AdSense slot per long page and by donations through the optional Chrome extension. That's it. Everything else — including this About page — is the same small group of people who built the tool because we needed it.