Privacy

• No tracking: this site currently uses no analytics, no advertising cookies and no third-party scripts.
• Your numbers stay on your device: every calculation runs in your browser. Nothing you type is sent to us or anyone else, and nothing you type is saved: no cookies, and your numbers are gone when you close the page. The only thing the site remembers is whether you chose light or dark mode, kept in your own browser. The site also tells your browser to block any attempt to send data from these pages, so this holds even if a script were changed by mistake.
• PDF downloads: the "Download PDF" button makes the file on your own device. The PDF is not uploaded or kept anywhere. PDFs are in English; Japanese characters are left out.
• Hosting: like any website, the hosting provider may keep standard server logs (such as IP address and pages requested) for security and operation. This site is hosted on Cloudflare Pages. Cloudflare processes requests under its own privacy policy. The operator does not receive or keep these logs.
• Contact form: if you send a message, we store the message and the email address you choose to give (if any) for up to 180 days, only to read and answer it. It is never shared or used for marketing. To prevent spam, a one-way hash of your connection address is kept for one hour; the address itself is not stored. Ask through the same form to have your message deleted sooner.
• Changes: if analytics or affiliate links are added later, this page will be updated first and will say what is collected.

Last updated: 6 October 2026 (prototype).