March 6, 2019 10:12 am

Announcing the Open Sourcing of Windows Calculator

Today, we’re excited to announce that we are open sourcing Windows Calculator on GitHub under the MIT License. This includes the source code, build system, unit tests, and product roadmap. Our goal is to build an even better user experience in partnership with the community. We are encouraging your fresh perspectives and increased participation to help define the future of Calculator.

Image of Windows Calculator

As developers, if you would like to know how different parts of the Calculator app work, easily integrate Calculator logic or UI into your own applications, or contribute directly to something that ships in Windows, now you can. Calculator will continue to go through all usual testing, compliance, security, quality processes, and Insider flighting, just as we do for our other applications. You can learn more about these details in our documentation on GitHub.

GitHub documentation of Windows Calculator

Open Contribution

In addition to reusing and adapting the code in your own apps, anyone can participate in the development of Windows Calculator. Getting involved is simple. The project is “clone-and-go” and development will follow the standard GitHub flow. There are many ways for developers at all stages to contribute:

  • Participate in discussions
  • Report or fix issues
  • Suggest new feature ideas
  • Prototype new features
  • Design and build together with our engineers


Reviewing the Calculator code is a great way to learn about the latest Microsoft technologies like the Universal Windows Platform, XAML, and Azure Pipelines. Through this project, developers can learn from Microsoft’s full development lifecycle, as well as reuse the code to build their own experiences. It’s also a great example of Fluent app design. To make this even easier, we will be contributing custom controls and API extensions that we use in Calculator and other apps, to projects like the Windows Community Toolkit and the Windows UI Library.

We are happy to welcome all of you to the Windows Calculator team! To get started, check out the Windows Calculator project on GitHub.

Updated March 6, 2019 3:33 pm

Join the conversation

  1. It’s probably outside the scope of this effort, but are there plans to migrate from C++/CX to C++/WinRT? Would be a great example for other developers.

  2. Please do the same for MS Paint! You increase its usability tenfolds by just implementing support for layers and transparent background.

  3. This is wonderful. We would like to contribute a posit mode with deferred rounding for folks to become familiar with the number system that is positioned to replace IEEE floating point. We have the posit arithmetic library available today, we would love to connect with folks that can help us think through the required changes to the UI.

    Interested parties can reach me through the posit library github repo:

  4. This is quite amazing to see, especially for myself, as I wrote the first version of this codebase for Windows 3 back in 1988-1989, during my first internship at Microsoft between my sophomore and junior years at the University of Washington. Seth Juarez did an channel9 interview with me about it all a couple years ago that people might find interesting: Honestly, though, I don’t recognize much of the code as I didn’t do anything with it after 1989.