Microsoft has recently open-sourced the Calculator app in Windows 10, and since the code is available on GitHub for any developer to contribute, it was pretty much just a matter of time until it ended up being ported to Android and iOS.
Uno Platform, which is a platform whose role is to enable C# and XAML code to run on mobile, desktop, and the web, ported the Calculator app to all of these, basically making it available for pretty much everyone regardless of device or operating system.
After porting the Calculator app to C# and to the Uno Platform, the team behind the project released it to the App Store for iPhones, the Google Play store for Android device, and on the web on this page for everyone to use.
On iPhone, however, the Calculator app is only available as part of the TestFlight program, so you need to register as a beta tester to be able to use it.
Calculator also available in the browser
“The Windows Calculator is an interesting and not-so-simple piece of software. The simple initial UI you see upon launch can be deceiving. Of course, that is a good UX choice Microsoft made as most uses of the calculator are rather simple ones. However, the calculator is…