Privacy policy

Last updated: 6 August 2026

Calc24 is a calculator that runs in your browser. Your calculations are performed on your own device and are never sent to us.

The short version

• There are no accounts, and we never ask for your name, address or payment details.
• What you type into the calculator stays on your device, in your browser’s local storage. We cannot read it.
• We collect anonymous usage statistics, and our host keeps standard server logs.
• We plan to show advertising. When we do, our advertising partners may set cookies. This policy already describes how that works.
• We do not sell or share your personal information.

Who we are

“Calc24”, “we” and “us” refer to the operator of calc24.org. You can reach us at info@def24.com for any question about this policy or about your data.

What stays on your device

The calculator saves your work locally so it is still there when you come back. That includes your open calculator tabs and their contents, your calculation history, pinned results, notepad lines, memory value, chosen theme and other preferences.

This is stored using your browser’s local storage. It never leaves your device and is not transmitted to us or to anyone else. You can erase it at any time by clearing site data for calc24.org in your browser settings; doing so resets the calculator to its initial state.

What we and our providers collect

Hosting and server logs

The site is hosted on Google Firebase Hosting. Like virtually every web server, it records technical information about requests — including your IP address, the time of the request, the page or file requested, your browser type and version, and the referring page. These logs are used to deliver the site, keep it available, and detect abuse or attacks. We do not use them to build a profile of you.

Analytics

We use Google Analytics (via Firebase) to understand, in aggregate, how the site is used — for example which calculator modes are popular and which devices and screen sizes we should support. This uses cookies or similar identifiers and may process a truncated or full IP address to approximate your country or region.

We do not send the contents of your calculations, notepad or history to analytics. If your browser sends a “Do Not Track” signal, we do not load analytics at all.

Advertising (planned)

We intend to fund the site with advertising, most likely Google AdSense. When advertising is enabled:

• Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this and other websites.
• Google’s use of advertising cookies enables it and its partners to serve ads to you based on your visit to this and other sites.
• You can opt out of personalised advertising by visiting Google Ads Settings, or opt out of third-party vendors’ use of cookies for personalised advertising at aboutads.info/choices and youronlinechoices.eu.
• Where the law requires it — in the European Economic Area, the United Kingdom and Switzerland — we will ask for your consent before setting advertising or analytics cookies that are not strictly necessary, and you will be able to change or withdraw that consent at any time.

Exchange rates

The unit converter can convert currency. To do that, your browser requests current exchange rates directly from a third-party service (open.er-api.com). That request contains no information about your calculation — only that a rate table was requested. The provider will see your IP address, as it would for any request your browser makes. If the request fails, or you are offline, the converter falls back to approximate rates bundled with the app and nothing is sent at all.

Installing the app

Calc24 can be installed as a progressive web app and works offline. Installing it stores the application files on your device. It does not grant us any additional access to your device.

Cookies and similar technologies

Local storage is used for your calculator data and preferences, as described above. Cookies and similar identifiers are used by analytics and, in future, by advertising. You can block or delete cookies in your browser settings; the calculator itself will continue to work normally.

Legal bases and your rights

Where the GDPR applies, we rely on our legitimate interest in operating and securing the site for server logs, and on your consent for non-essential analytics and advertising cookies. Depending on where you live, you may have the right to access, correct, delete or port your personal data, to object to or restrict processing, to withdraw consent, and to complain to your local data protection authority.

Residents of California and other US states with comparable laws have the right to know what personal information is collected, to request deletion, and to opt out of “sale” or “sharing” of personal information. We do not sell personal information, and we do not share it for cross-context behavioural advertising except as described in the advertising section above.

Because we do not operate accounts, we usually cannot identify which log entries or analytics records relate to you. If you contact us at info@def24.com we will help as far as we reasonably can, and may ask for information needed to locate the relevant records.

Data retention

Data stored on your device stays until you clear it. Server logs and analytics data are kept by our providers for their standard retention periods and are then deleted or aggregated.

International transfers

Our hosting, analytics and advertising providers operate globally, so the limited data described above may be processed in countries other than your own, including the United States. Those providers use recognised transfer mechanisms, such as the European Commission’s standard contractual clauses.

Children

This site is a general-purpose calculator and is not directed at children under 13 (or the equivalent minimum age where you live). We do not knowingly collect personal information from children. If you believe a child has provided us with personal information, contact us and we will delete it.

Security

The site is served over HTTPS with a strict content security policy, and it requests no permissions from your device beyond optional vibration for key presses. No method of transmission or storage is completely secure, but because we hold so little, there is very little to lose.

Third parties we rely on

• Google Firebase Hosting — serving the site
• Google Analytics — aggregate usage statistics
• Google AdSense — advertising (planned)
• open.er-api.com — currency exchange rates, requested only when you use the converter

Each has its own privacy policy governing how it handles data it receives.

Changes to this policy

We will update this page when the site changes — in particular before enabling advertising or any feature that sends data to a server. The date at the top always reflects the most recent substantive revision.

Contact

Questions, requests or complaints: info@def24.com.