There is no account to make and nothing to sign up for. The calculators run entirely in your browser, so the numbers you type are worked out on your own machine and never sent anywhere.
One thing. Tapping ♥ writes that calculator's name into your browser's own storage, so the shortcut is waiting next time. It stays on that device, it never reaches us, and clearing your browser data removes it.
No analytics, no advertising, no cookies, and no third-party scripts of any kind. Nothing on these pages loads from another company's server.
GitHub serves these pages, and like any web server it sees the requests that reach it: the address they came from and the browser that made them. That is GitHub's, under their privacy policy. We neither collect it nor hold it.
Then we have your address and whatever you wrote, and nothing else. It is used to reply to you.
If this ever changes — if the site carries advertising, for instance — this page changes first.