About
About pctzen
PctZen is a small, independent project. A percentage calculator is the whole of what we do here: it answers percent-of, what-percent, and percent-change questions instantly, with a discount and tip mode. There is no account to create, no email to hand over, and no paywall hiding behind the third advert.
Why this site exists
Most everyday-utility tools online spend more screen space on advertising and consent banners than on the calculation. PctZen takes the other approach — the tool does one thing, answers percent-of, what-percent, and percent-change questions instantly, with a discount and tip mode, and the page stays out of the way while it does. A narrow scope is easier to keep correct, too.
How the result is produced
No server is involved in the arithmetic. It picks the right rearrangement of the percentage relationship for the question you ask — part over whole, or the difference over the original — so the same tool covers a markup and a discount without the sign confusion. We state the method openly because a tool that cannot explain its own answer is not much use to anyone trying to trust it.
What happens to your input
The numbers you enter never leave your browser. There is no backend that receives them, no database that stores them, and no advertiser that sees them — so you can load the page, disconnect from the internet, and the tool keeps working.
Who it is for
- people who need one clear answer fast.
- users on a phone with a slow connection.
- anyone tired of sign-up walls on a simple tool.
How this stays free
Advertising pays for the running of PctZen; nothing here is subscription-based. No advertiser is given the values you enter, and an advert appearing beside a tool is never a recommendation of it.
Tell us what you think
Spotted a mistake or missing a feature? The contact page takes it. The suggestions that get acted on usually come from people who actually use the percentage calculator.