Privacy policy
First published 27 August 2026. Updated .
Sumi is an independent scientific calculator made by Tomu Ozawa. Calculations work offline. The app has no account system, advertising, analytics or crash-reporting service, and does not send your calculations or local usage records to the developer.
Data stored on your device
Sumi saves calculation history, memory values, the expression being edited, calculation settings, and appearance and control preferences in the app’s local storage. It also saves support history and a small amount of information used to space out review requests, described below. On Android, it records the dates used to time the one-time Quick Settings tile offer and what you chose.
Sumi does not operate a server that receives this information. Your operating system may include local app data in device backups or transfers, depending on your device and account settings. Those services are controlled by the platform provider.
Text from other apps
Sumi reads text only when you ask it to: when you use Paste and Calculate, choose Calculate in another app’s text menu, run the Calculate action in Shortcuts, or paste with a keyboard or the Edit menu. When you use Paste and Calculate, iOS asks before Sumi reads text copied in another app. Sumi checks the text on your device. A sum becomes the current calculation and joins your history, and anything else is discarded. Copying an answer puts it on your clipboard.
Clearing your data
Open Settings → Calculation → Memory & reset → Reset calculator to clear memory, calculation history and the current expression, and restore default calculation settings. This keeps appearance and control preferences, support history, review request timing information and the tile offer record.
To remove all local Sumi data, use your device’s app storage controls or delete the app and its data. Device backups, store purchases and public reviews are managed separately through the relevant platform.
Tip jar purchases
Tips are optional one-time purchases and unlock no features. Google Play or the App Store handles payment through its billing service. The app receives purchase status and product and transaction identifiers, and stores a local tip count and transaction record so each purchase is counted once. It does not receive your payment card details, name or email address from the purchase.
The store provides the developer with sales and financial reports. When Sumi opens, store billing connects to the internet to load tip prices and finish any pending purchase, and it connects again when you leave a tip. On Android, Google’s billing library may also send Google diagnostic information about the billing service. Apple’s and Google’s handling of store data is described in the Apple Privacy Policy and the Google Privacy Policy.
Review requests
Sumi stores a limited calculation count, a few dates when calculations were completed, when review timing began, and dates of review request attempts or the Rate Sumi action. This information stays in local preferences and helps the app avoid asking for a review too early or too often. It is not sent to an analytics service or the developer.
Review prompts use the platform’s own review service. The app is not told whether you submitted a review or what rating you chose. If you submit a store review, it is handled and may be published by Google or Apple under their policies. The developer can see public reviews and aggregate store reports.
Links, sharing and support email
Guides, support and privacy links open this website in your browser. Rate Sumi opens the store listing. Share Sumi opens your device’s share sheet with a download link; Sumi does not choose recipients or send a message automatically.
If you email the developer, your email address, message and any attachments you choose to send are received so your request can be answered. Cloudflare forwards messages to a Gmail inbox, where Google stores them. The in-app feedback action prepares an editable email with the app version and platform. You decide whether to send it.
This website
This website uses no visitor analytics, cookies or advertising scripts. Fonts and images are served with the site. Its interactive examples and animation controls work in your browser; they send nothing anywhere and aren’t saved.
Google Play links contain campaign labels identifying this website and the referring page. These labels contain no personal identifier. Google processes visits and downloads under its own policies. Google Search Console and store reports can provide aggregate information about search discovery and download interest.
The website is hosted on Cloudflare. Cloudflare processes information needed to deliver pages, such as IP addresses. See the Cloudflare Privacy Policy.
Children
Sumi is suitable for a general audience. The app does not ask for age or other personal details, and the developer does not knowingly collect personal information from children. If a child has sent personal information by email, contact the developer to request its deletion.
Your rights
Tomu Ozawa is responsible, as controller, for the personal information described here: emails you send, store sales reports and the delivery of this website. Under UK and EU data protection law, it’s handled on these bases:
- answering your email and running and securing this website: legitimate interests;
- keeping sales and financial records: legal obligation.
Emails are kept while they’re needed to answer you and follow up, then deleted. Sales records are kept for as long as tax law requires. Cloudflare keeps its logs under its own policy.
Apple, Google and Cloudflare may process information in the US and other countries. Those transfers rely on safeguards such as the UK–US data bridge or standard contractual clauses.
You can ask to see, correct or delete your information, to restrict or object to its use, or to receive a copy, by emailing hello@sumicalculator.com. You can also complain to the Information Commissioner’s Office or your local data protection authority.
Changes to this policy
If Sumi’s behaviour changes in a way that affects your privacy, this page will be updated and the revision date above changed.
Contact
Questions about this policy can be sent to hello@sumicalculator.com.