The calculator you know from school
About this app
This is a very early version in development. Unlabeled buttons will be implemented in the future, and bugs may be frequent. If you experience issues or have feature requests, please file an issue (link below).
Frustrated by the lack of free, open-source scientific calculators that feel like the ones I am used to, I decided to reverse-engineer my old calculator from school.
With features like:
- input of complex equations,
- output as fractions as well as decimals,
- result storage and reuse,
- selection and editing of equations from input history,
- and support for implicit multiplication (like 5π instead of 5*π),
this calculator produces math that looks like the math on your paper. That makes it much more suitable for higher-level math in school and university—especially if you've grown accustomed to this kind of interface from a young age and just forgot your calculator at home.
Some additional features include:
- A well-established open-source math.js library as the math engine—so you’re not relying on some sketchy, hand-rolled math logic (just my sketchy hand-rolled input method 😛)
- A familiar, intuitive design
- 100% offline usability and fully open source
- Written entirely in HTML, JS, and CSS, which means:
+ inherently cross-platform and also available as a website and Flatpak
+ easy for other web developers to contribute
+ admittedly a bit heavy for a calculator. If you're interested in helping make a lighter version (Flutter, Kotlin, etc.), you're very welcome!
Licensed under GPL-3.0-only, by Joris Yidong Scholl.
What's New in v1.15.0
Imported from the F-Droid repository index.
- Feature: Added % function
- Feature: Added ON-button
- Feature: Added OFF-button
- Feature: Added Setting to toggle Turn-Off = Close App
- Feature: Web Version can now be installed as a PWA
- Bugfix: (19/21) / (2/7) now results in a fraction
Version history
Jun 9, 2026 · 3.3 MB · Android API 24–36 · code 11500
Imported from the F-Droid repository index.
- Feature: Added % function
- Feature: Added ON-button
- Feature: Added OFF-button
- Feature: Added Setting to toggle Turn-Off = Close App
- Feature: Web Version can now be installed as a PWA
- Bugfix: (19/21) / (2/7) now results in a fraction
SHA-256 bb05221904723b7c1fc5f0f8cd6645231fddfc42ba64c12815b0b418a1d62e22
Jan 26, 2026 · 3 MB · Android API 24–35 · code 11400
Imported from the F-Droid repository index.
- Feature: °′‴-button now switches to DMS format
- Feature: Added option to toggle between Deg, Rad and Gra angle modes
- Feature: Added Eng-button for engineering notation
- Tweak: Updated dependencies
SHA-256 1083705dd4e14728187b223154ec20d4b04829e7b5ac1e8f6307342290b4750c
Oct 10, 2025 · 3 MB · Android API 24–35 · code 11200
Imported from the F-Droid repository index.
- Feature: Added config option to prefer decimal results
- Feature: Added mode menu
- Feature: Added CMPLX mode and i
- Feature: Added integration
- Feature: Added differentiation
- Feature: Added setup menu
SHA-256 572dc6b8648bd527b66c0c5ac67e1446673c8d9bc5c622abb4347f822d061b34
Will it run on your device?
78%
- Runs on a broad range of modern Android versions.
- ABI coverage is focused on newer 64-bit devices.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be io.cardijey.schulrechner is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 1.14.0 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall Schulrechner first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of Schulrechner, and a listing is removed when the evidence for it stops holding up.
Get Schulrechner
Every source we list for io.cardijey.schulrechner is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
bb05221904723b7c1fc5f0f8cd6645231fddfc42ba64c12815b0b418a1d62e22
Signing certificate
68ab652b4d4fab1a6890ccb449b1f79e6c6cb0a08107cb436a25903818765098
Permissions Required
What each permission lets Schulrechner do. A highlighted one is worth a second look — not necessarily wrong, just worth asking whether this app needs it.
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
More Education apps
More from F-Droid
Report a problem with this listing
A listing is only as good as its corrections. If a source is broken, a signature looks wrong, or this app should not be here, tell the moderation team.