Privacy policy

Calx, last updated 13 September 2026

Calx does not ask who you are. There is no account, no sign in, and no name, email or phone number anywhere in the app. Almost every calculation is worked out on your own device and never leaves it.

What Calx works out on the device

Arithmetic, percentages, unit conversions and everything the app can recognise on its own are calculated entirely on your phone or tablet. Nothing about those questions is sent anywhere.

Your history of questions is stored on the device only. Clearing it removes it. We never receive a copy.

What is sent, and when

When you ask something the app cannot work out on its own, the text of that one question is sent to our server, which passes it to Anthropic to be turned back into a calculation. The calculation is then performed on your device.

Only that question text is sent. Not your history, not your other questions, not anything about you.

⚠️ People type real figures into calculators. Please treat the app the way you would treat any tool connected to the internet and avoid typing anything you would not want leaving the device.

The device identifier

To count how many interpretations a device has used each day, Calx creates a random identifier of sixteen bytes the first time it runs and stores it on the device.

• It is not an advertising identifier
• It is not taken from your hardware
• It does not survive uninstalling the app, and reinstalling creates a new one
• It means nothing outside our own usage table

This is deliberate. An identifier strong enough to survive a reinstall would be strong enough to follow a person around.

Voice input

If you speak your question instead of typing it, the audio is handled by the speech recognition built into your phone, which is Apple's on iOS and Google's on Android. Their handling of that audio is governed by their own privacy policies, not this one. Calx receives only the resulting text.

The microphone is used only while you are actively dictating. It is never listening in the background.

Crash reports

If the app crashes, a technical report is sent to Sentry so the fault can be fixed. It contains the error and where in the code it happened.

Personally identifying data is switched off, so IP addresses are not attached. The app also switches off the feature that would record what you tap and type, because a typed question could otherwise arrive attached to an unrelated crash.

Usage measurement

Calx records four events through PostHog so we can tell whether the app is being used. The list is fixed in the code and nothing can be added to an event.

The text of your questions is never sent to analytics. Not as a property, not as a label, not in any form.

Purchases

Subscriptions and the one time unlock are handled by Google Play or the App Store, and by RevenueCat which keeps track of whether a device has an active purchase.

We never see your card, your billing address or your store account. Your purchase is attached to the same anonymous device identifier described above, not to a person.

What Calx never does

• No advertising, and no advertising identifiers
• No selling or sharing of data with data brokers
• No location, contacts, photos, calendar or files
• No accounts, and no email or phone number collected
• No tracking across other apps or websites

How long anything is kept

Daily usage counts are kept only as long as they are needed to enforce the free daily allowance. Interpretations may be cached briefly so that the same question asked twice does not cost a second lookup. Crash reports follow Sentry's retention period.

Your question history lives on your device and is deleted when you clear it or remove the app.

Children

Calx is a general purpose calculator and is not directed at children. We do not knowingly collect information from children, and since we collect no personal information at all there is nothing held about any user of any age.

Your rights

Because Calx holds no personal information, there is no account to access, correct or delete. If you want the anonymous usage count for your device removed, uninstalling the app abandons that identifier permanently, and reinstalling creates a new one.

If you would still like to make a request, write to us at the address below and we will answer.

Changes

If this policy changes, the date at the top changes with it. Material changes will be announced in the app before they take effect.

Contact

Questions about this policy can go to [email protected].