Privacy Policy

Last updated May 2, 2026

In short

Calc Center does not require an account and does not sell or share user-level data. Every calculator runs in your browser. The data you type stays on your device unless youshare a link or print/PDF the result. We use Google Analytics to count visits and understand which calculators are used — details below.

What we store on your device

• Theme preference (localStorage:theme) — light or dark.
• Display currency (localStorage:calccenter:currency).
• Favorites (localStorage:calccenter.favorites) — a list of slugs you starred.
• Recent (localStorage:calccenter.recent) — the last calculators you opened.
• Saved scenarios (localStorage:calccenter.scenarios) — named snapshots of calculator inputs.
• URL state — your current calculator inputs are reflected into the address bar so a copy/paste is a working share link.

Clearing site data in your browser deletes all of the above. None of it leaves your device.

Server-side requests

Calc Center is a static-rendered Next.js application. Pages are served as pre-built HTML and JavaScript. Two server endpoints exist:

• /api/fx — returns currency exchange rates. Cached at the edge for 6 hours; no per-user data attached.
• /api/explain— optional plain-English explanation of a calculator's result. The prompt and result you submit are forwarded to Anthropic's API to generate text. No personally identifying information is included unless you typed some into the calculator. Subject to a per-IP rate limit.

Cookies

Google Analytics sets two first-party cookies in your browser (_ga and _ga_<container-id>) to count unique visitors and sessions. They expire after roughly 13 months. The geo-aware income-tax landing page may set a single non-tracking cookie (tax-country) when you explicitly pick a country, so we remember your choice on the next visit.

Analytics

Calc Center uses Google Analytics 4 to measure aggregate traffic — page views, referral source, country, device type, and which calculators are popular. Your IP address is anonymized (anonymize_ip) before storage, and we have not enabled Google Signals or ad personalization. We do not pass any inputs you type into a calculator to Google Analytics. You can opt out by installing the official Google Analytics opt-out browser add-on or by blocking third-party scripts in your browser.

Third-party services

• Google Analytics — aggregate traffic measurement, as described above.
• Frankfurter (ECB) — Calc Center fetches reference exchange rates from the European Central Bank's public dataset via Frankfurter. Calc Center's server makes the request, not your browser.
• Anthropic — only when you click an explain button on a calculator and the operator has configured an API key.

Your rights

Because Calc Center does not collect personal data, there is generally nothing for us to delete on your behalf. You can clear all Calc Center-related data by clearing your browser's site storage for this domain.

Contact

Questions about this policy? Contact us.