Privacy Policy for FormulaGrid

App: FormulaGrid: Calculator Package name: com.mobilecastle.formulagrid Publisher: MobileCastle (Mobile Castle) Effective date: 29 October 2026

This policy is for the free version of FormulaGrid, which offers no in-app purchases.

This Privacy Policy explains what information the FormulaGrid app (“FormulaGrid”, “the app”, “we”, “us”) does and does not handle, and how. Please read it together with the policies of the third parties named below.

By using FormulaGrid you agree to the practices described here.

Summary (plain language)

• FormulaGrid has no user accounts and no sign-up. We do not ask for your name, email, phone number, or any similar personal detail.
• Your calculations stay on your device. Every calculation runs on your phone or tablet, without the internet, and your history, favorites and saved scenarios are stored only there; a result leaves your device only when you share it. Mobile Castle does not operate any server that receives them.
• FormulaGrid needs no special permissions: no camera, microphone, location, contacts or storage access.
• FormulaGrid shows ads through Google AdMob, a third party. To serve ads, AdMob may collect device information and an advertising identifier. Ads never receive your calculations, inputs or results.
• No purchases in this version. FormulaGrid offers nothing to buy: it does not connect to Google Play Billing, and it does not ask for the billing permission. Premium features are coming soon.

The rest of this policy gives the detail behind that summary.

Information FormulaGrid itself collects

FormulaGrid does not collect personal data on its own servers, because Mobile Castle does not run a server that receives your data. Specifically:

• No account / identity data. There is no login, so we do not collect a name, email address, password, phone number, or profile.
• No upload of calculations. The numbers you enter, your results, history and scenarios are not copied to us.
• No analytics SDK operated by us. FormulaGrid does not embed our own analytics, crash-reporting or tracking service. (Google AdMob and the other Google services described below are independent third parties with their own data handling.)

Data that stays on your device

Some information is stored locally on your device so the app can work and remember your settings. This data is not transmitted to Mobile Castle, and it is excluded from Android’s cloud backup. It includes:

• History: the calculations you finish: the keypad’s expression and its result, or a calculator’s inputs, the formula version and its result, with the date. They are saved in a database in the app’s own private storage. This version shows the latest twenty entries; older ones stay on your device, locked, and are never deleted on their own.
• Favorites, recently used calculators and saved scenarios: the calculators you star or opened last, and the sets of inputs you name and save.
• Your preferences: for example theme, language, units, currency symbol, thousands separators, haptic feedback, the angle unit, the last inputs of each calculator, and the keypad’s current expression and memory.
• A local diagnostic log: FormulaGrid writes a technical log (which features started, errors) to a file in the app’s own folder on your device, to help troubleshoot problems on real hardware. It never contains your calculations, inputs or results, and it stays on your device unless you deliberately share it.

All of it is removed when you uninstall FormulaGrid. Settings → Clear history removes your history, and Clear all local data removes history, scenarios, favorites and settings. See Data retention and deletion below.

When you share a result or a table, Android’s share sheet sends it, as text, to the app you choose (for example a messaging app). What that app does with it is governed by its own privacy policy.

Advertising (Google AdMob)

FormulaGrid is free and supported by ads served through Google AdMob, a Google service. Ads appear as banners in the Library and History lists and below full result tables (for example the complete amortization schedule), never on the calculator keypad, next to the fields you type in, in the formula editor or on an advanced calculator’s offer screen. There are no full-screen ads when you open the app or move between screens.

The ad requests FormulaGrid sends carry no content from the app: no calculation, input, result, scenario or formula is ever passed to AdMob. To select and show ads, Google AdMob (and the Google Mobile Ads SDK included in the app) may collect and process information such as:

• a device advertising identifier (Android Advertising ID),
• device and network information (for example device type, operating-system version, approximate location inferred from your IP address, and similar technical data),
• ad-interaction and app-usage data related to the ads shown,
• crash and diagnostic information about the ads software itself.

Google uses this information to serve and measure ads and to help prevent fraud and abuse, in accordance with Google’s own policies. Where required by law (for example, for users in the European Economic Area, the UK and Switzerland), FormulaGrid uses Google’s User Messaging Platform to show a consent form before serving personalised ads, and no ad is requested until that choice is made; you can change your choice at any time in Settings → Privacy options. You may also choose to watch a short rewarded ad to use one advanced calculator until you close the app; this is optional, and the app says what the ad unlocks before it plays.

• Google Privacy Policy: https://policies.google.com/privacy
• How Google uses information from sites or apps that use its services: https://policies.google.com/technologies/partner-sites
• AdMob / Google Ads policies: https://support.google.com/admob/answer/6128543

You can limit ad personalisation and reset your advertising ID in your device settings (Settings → Google → Ads on most Android phones).

Purchases

This version of FormulaGrid offers no in-app purchases. It does not connect to Google Play Billing, and no part of the app can start a payment. It asks for no billing permission. Features planned for a future Premium version show “Premium features are coming soon.” If purchases are added in a later version, this policy will be updated before that version is released.

App permissions and why they are needed

FormulaGrid requests the following Android permissions. Each is used only for the feature described:

• Internet (INTERNET): to load ads. Calculations are not sent.
• Network state (ACCESS_NETWORK_STATE): to check whether you are online before loading an ad.
• Added by the Google libraries: the advertising ID and Android’s privacy-preserving ad APIs (AD_ID, ACCESS_ADSERVICES_AD_ID, ACCESS_ADSERVICES_ATTRIBUTION, ACCESS_ADSERVICES_TOPICS) for ads; and background-work permissions (WAKE_LOCK, RECEIVE_BOOT_COMPLETED, FOREGROUND_SERVICE) that the Google libraries use for their own short tasks.

FormulaGrid asks for no camera, microphone, location, storage, contacts, phone or SMS permission.

Third-party services

FormulaGrid relies on the following third parties. Their handling of information is governed by their own privacy policies:

Children

FormulaGrid is a general-audience utility and is not directed at children. We do not knowingly collect personal information from children. The app is intended for general audiences and, in line with the store listing, is not aimed at or designed to appeal to children.

Because the app shows ads, it follows Google Play’s Families and ads policies for a general-audience app. If you believe a child has used the app in a way that raises a concern, please contact us using the details below.

Data retention and deletion

Data stored locally by FormulaGrid (history, favorites, scenarios, preferences and the diagnostic log) stays on your device and is retained until you remove it. FormulaGrid never deletes your history on its own: this version shows the latest twenty entries and keeps the rest on your device, locked, not deleted.

You can delete this data at any time by:

• uninstalling the app, which removes all of its local storage, or
• using Settings → Clear history (all history) or Clear all local data (history, scenarios, favorites and settings), or deleting a single history entry or scenario.

Mobile Castle does not hold a copy of this data, so there is no separate server-side deletion request to make to us.

For data processed by the third parties above (for example Google’s advertising data), please use the controls those parties provide (see their policies linked above) and your device’s Ads settings.

Security

Because FormulaGrid keeps your data on your own device and does not run a Mobile Castle server, your calculations are not exposed on our infrastructure. They leave your device only when you share them.

No method of electronic storage or transmission is 100% secure; while we aim to protect your information, we cannot guarantee absolute security.

Changes to this policy

We may update this Privacy Policy from time to time, for example if the app adds a feature that changes how information is handled. When we do, we will update the Effective date above and post the revised policy at the URL where this policy is hosted. Significant changes may also be noted in the app or its store listing.

Contact

If you have questions about this Privacy Policy or FormulaGrid’s data practices, you can contact us at:

• Email: mobilecastle.android@gmail.com
• Publisher: MobileCastle (Mobile Castle)