What the instruments do with your inputs
Nothing, beyond arithmetic. Every calculation runs in your browser, in the page you're looking at, at the moment you type. No figure you enter is transmitted, logged, stored or seen by anyone — including us. Close the tab and the numbers are gone.
Accounts
There are none. Nothing on this site requires registration, and nothing is gained by offering it. Arithmetic should not need your email address.
Cookies and storage
One item of local storage: your day/night theme preference, kept on your device so the site remembers which desk you read at. It contains the word "day" or the word "night". That is the complete inventory.
Analytics and advertising
No analytics scripts, no advertising networks, no pixels, no fingerprinting, no third-party requests beyond the typefaces. The site loads its fonts from Google Fonts, which — like any host — sees the technical request your browser makes to fetch a file; if that bothers you, the site remains fully legible in your system's fallback fonts with fonts blocked.
Server logs
Whatever host serves these static files keeps ordinary access logs — the page requested, a timestamp, an IP address — as every web server has since the beginning. These are used for keeping the site standing and for nothing else. They never contain anything you typed into an instrument, because what you type is never sent.
Changes
If any of the above ever changes, this page changes first and says so at the top, dated. Silence here means the sentence at the top still holds.