About ITCalcTools.com
I'm a systems administrator and cloud engineer. I've been doing this for close to 30 years now — long enough to have worked through dial-up modems, physical server racks, the move to virtualisation, and now the endless sprawl of cloud infrastructure. In that time I've built up a mental list of the calculations and lookups I reach for constantly: subnet math, hash generation, DNS checks, cron expressions, SPF/DMARC records, CVSS scores, the list goes on. None of it is complicated on its own. What's annoying is where it all lives.
The actual reason this exists
Before this site, my bookmarks folder was a graveyard of a dozen different single-purpose tool sites — one for subnet calculations, a different one for hash generation, another for JSON formatting, another for checking DNS propagation, most of them cluttered with pop-ups, some asking me to sign up just to use a calculator, a few that quietly stopped working and I didn't notice for months. Every time I needed something slightly outside my usual rotation, it was another search, another unfamiliar site, another few seconds of "is this one trustworthy." That adds up over a career. I got tired of it and started building the tools I actually use, one at a time, in one place I control.
That's it, honestly — that's the whole origin story. Not a grand plan to build a SaaS product. A working sysadmin who wanted his own tools in his own place, built to the standard he'd actually want to rely on at 2am during a change window.
How the tools are actually built
Everything on this site runs entirely in your browser. When you calculate a subnet, hash a file, decode a JWT or check DNS propagation, that work happens on your machine — nothing gets sent to a server for processing. I built it this way partly because it's simpler to host and partly because it's the only version of "trust me" that doesn't actually require you to trust me: you can open your browser's dev tools and watch that nothing sensitive leaves your machine. The one deliberate exception is the "email these results" feature on some tools, which is opt-in and explained in the privacy policy.
I don't cut corners on the actual logic either — cryptographic functions use the browser's native Web Crypto API rather than a hand-rolled implementation, the CVSS calculator follows the official FIRST.org scoring formula exactly, the cron parser handles the genuinely confusing day-of-month/day-of-week OR-logic correctly instead of the simplified version most tools fake, and so on. If a tool gives you a wrong answer, that's a bug I want to know about, not an acceptable trade-off for shipping fast.
Why it's free, and why there are ads
The tools are free with no account, no paywall and no artificial limits — that was never up for debate. Hosting and the time to keep building and fixing this isn't free on my end though, so the site carries a small amount of advertising to cover that. I've kept it to one sidebar slot and one inline slot per page, clearly labelled, and I have no intention of letting that creep into something that gets in the way of the actual tools. If you use an ad blocker, that's fine too — everything still works exactly the same.
What's next
More tools, mostly — I keep a running list of the things I reach for at work that aren't on here yet, and I add them in batches. If there's something you use regularly that's missing, or you spot a tool giving you an answer that doesn't look right, I'd genuinely like to hear about it. See the privacy policy for a contact address.