Every developer I know has the same five tabs permanently open. A JSON formatter from some site that loads three cookie banners before the textarea appears. A Base64 encoder that's been running on a 2009-era PHP server. A unit converter that requires an email address for no obvious reason. A percentage calculator buried under a wall of AdSense. And a spreadsheet they opened last Tuesday and forgot to close.
We've normalised this. We've accepted that reaching for a basic tool means either tolerating a terrible experience or building one ourselves. I got tired of both options.
So I built The Calcu.
Not a single tool. Not a focused niche product. Four hundred and thirty-four tools across calculators, converters, generators, formatters, and validators. Finance, tax, health, math, marketing, developer utilities, and everyday calculations, all in one place with no login, no paywall, and no data leaving your browser.
The case for breadth over niche
The conventional product advice is to pick one problem and go deep. I thought about that seriously. But when I mapped out how I actually use calculator-type tools in a day, I don't have one recurring need. I have twelve unrelated ones: compound interest this morning, a JSON diff this afternoon, a word count before I send a draft, a GST check before I raise an invoice. Building a single niche tool would have solved one of those and left the other eleven pushing me toward competitors.
The constraint I set was that every tool had to load instantly, update in real time as you type, and never require an account. If I couldn't ship it to that standard, I didn't ship it. That discipline kept the breadth from becoming bloat.
The architecture decision that made this possible
All calculations run entirely in the browser. Nothing is sent to a server. This is partly a privacy decision, partly a performance decision, and partly the reason the whole thing stays free to run at scale. When there's no server-side compute to bill, the cost model stays clean and the tool stays free forever.
URLs encode calculation inputs automatically. If you run a compound interest calculation with specific values, the URL updates to reflect those inputs. You can share it as-is, bookmark it, or send it to a colleague, and they land directly in your calculation state. No "copy results" button, no export, no sharing modal. The URL is the share mechanism.
The developer tools, specifically
The part of the platform I use most in my own workflow sits under the Formatters and Validators categories. The JSON formatter handles minification and prettification, validates structure, and highlights errors with line references. The Base64 encoder and decoder handles both standard and URL-safe variants. The validators cover a wide range of formats: email, URL, IP address, UUID, IBAN, credit card structure, and a handful of region-specific formats I added because they were missing everywhere else.
These aren't tools I built to round out a portfolio. They're tools I was actually using other sites for and wanted under one roof.
What's still missing
The site launched a month ago
If you find a tool that's returning a wrong result, or a calculation type you'd expect to find and can't, I genuinely want to hear it. The tools are only useful if they're accurate, and at 434 tools, there are almost certainly edge cases I haven't caught yet.
The platform is at thecalcu.com No account needed to use any of it.
What tool do you wish existed? Leave you comments and I am happy to build one.
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