Support & FAQ

The same way as the calculator that comes with your phone:

• With + and −, % adds or subtracts that percentage of the first number: 200 + 10% = 220, 200 − 10% = 180.
• With × and ÷, it means “percent of”: 200 × 10% = 20, 50 ÷ 10% = 500.
• On its own it divides by 100: 50% = 0.5.

You can read all the rules in the app under Settings → Calculation Rules.

The last operation is repeated: 2 + 3 = = = gives 5, 8, and 11, and each result is saved to your history.

Sumbox performs addition, subtraction, multiplication, and division with exact decimal arithmetic and shows up to 15 significant digits, so you never see the tail of a binary floating-point number. Functions such as trigonometric functions and logarithms are calculated first and then rounded to 15 significant digits for display.

The rates come from the Frankfurter public exchange rate service, which aggregates public data from central banks and similar sources and is updated once a day. They are reference rates: not the RMB central parity rates published by the People’s Bank of China, and not the real-time rates of banks or payment platforms. For an actual exchange, the rate quoted by your bank or platform applies.

Sumbox sends only currency codes to the rate service, never the amounts you enter. Retrieved rates are cached on your device, so the last rates remain available offline, and the page shows the date of the data.

• Make sure your device is online and that Sumbox is allowed to use Wi‑Fi and cellular data in iOS Settings.
• Tap refresh on the currency page to try again; in some networks, services outside mainland China can be slow to reach.
• Everything else runs on your device and is not affected. If the rates still won’t load, write to us with your network provider and region.

Mint and Clear Contrast are always free. You can try on every other theme in full under Calculator → Settings (top right) → Themes & Icons, and when you like them, unlock them with the in-app purchase “Unlock All Themes”: buy once and keep it forever, with themes added later included at no extra charge. It never renews automatically. The price shown in the App Store applies.

1. Make sure you are signed in to the App Store with the Apple Account you used for the purchase.
2. Open Sumbox and go to Calculator → Settings (top right).
3. In the Purchases section, tap “Restore Purchases” and wait a moment for the themes to unlock again.

Restoring never charges you again. If you see “No purchases to restore”, check that you are using the right account, or write to us.

Yes. “Unlock All Themes” supports Family Sharing: once Family Sharing and Purchase Sharing are turned on, members of your family group can open Sumbox on their own devices and use the themes, tapping “Restore Purchases” once if needed.

All App Store payments and refunds are handled by Apple; you can request a refund at reportaproblem.apple.com. After a refund the paid themes stop working and Sumbox switches back to Mint automatically; your history is not affected.

Key sounds follow your phone’s silent mode and are muted while it is on. Turn off silent mode or raise the volume and try again. Haptics can be switched on and off separately in Settings.

Your history and settings are stored only on your device; Sumbox has no accounts and uploads nothing. History is kept in the app’s own file (Application Support/History/history.json) and settings in the system preferences store.

• Delete one entry: on the History page, swipe left on the entry, or touch and hold it and choose “Delete”.
• Clear everything: on the History page, tap More (⋯) → “Clear All History”.
• Deleted by mistake? For a few seconds after deleting or clearing, tap “Undo” in the banner at the top.
• Export: in the More menu you can export your history as text or as a CSV spreadsheet.
• Delete everything: deleting the Sumbox app also removes all data it stored on your device.

If iCloud Backup is on, this data may be included in your device backup in iCloud, which is managed by Apple.

Sumbox includes no advertising, analytics, or tracking tools, requests no location, camera, or contacts permission, and does not upload your calculation history. Online services, purchases, website visits, and support emails you choose to send involve their own data handling. See the Privacy Policy for details.

Calculation, Chinese Family Titles, and most tools work offline. These features use a network connection:

• Exchange rates: when you open the currency converter or tap refresh, Sumbox fetches reference rates from the Frankfurter public exchange rate service, sending only currency codes and never amounts.
• Update checks: no more than once a day, Sumbox asks Apple’s App Store whether a new version is available, sending only the app identifier and the App Store region code, without sending calculation history. There is no automatic check on the day you first use the app.

Purchases, restoring purchases, and theme entitlement validation use Apple StoreKit and may connect to Apple services. Opening the website or App Store, or sending email, uses the relevant service. Network requests may include information such as your IP address; see the Privacy Policy.

When a new version is available, you only see a notice you can dismiss (“Update in the App Store”, “Later”, “Skip This Version”), and you can keep using the app without updating. To stop the automatic checks, turn off “Check Automatically” under Settings → Updates (the button at the top right of the calculator); tap “Check for Updates” whenever you want to check yourself.

No. The kinship algorithm and dictionary are installed with the app and run on your device, so your family relationships are never sent anywhere.