Keys and unlocks

Every calculator on this site is free, and every answer it works out is free, on every device, with no sign-up. Two small things are not: a pass that keeps the ad off your printouts, and the reference charts bundled as one printable document. Between them and the shop links, they are what pays for the site.

How a key works

Checkout happens on the shop's own page — nothing about your card comes anywhere near this site, because there is no server here for it to come near. The shop sends you a key. Typing it above tells this browser to stop showing you the thing you paid to be rid of, and the key is kept in this browser the same way a saved job is.

That means it works offline, in a shop with no signal, on as many of your own devices as you like — and that clearing site data clears it, exactly as it clears your saved jobs. So keep the email. It is the only copy of the key that this site cannot lose for you, and there is no account to recover it from.

Being straight about the other half: the check happens in your browser, so a key is a receipt rather than a lock, and anybody determined could get past it. Building a real one would mean accounts, a server and a login in front of a tool people open with sawdust on their hands — which would cost more than it protects and make the site worse. This is the trade, and it is the same one behind everything else on the privacy page.