Calc.exe is now open source; there’s surprising depth in its ancient code (2019)

This page summarizes the projects mentioned and recommended in the original post on

Our great sponsors
  • Scout APM - Less time debugging, more time building
  • OPS - Build and Run Open Source Unikernels
  • SonarQube - Static code analysis for 29 languages.
  • calculator

    Windows Calculator: A simple yet powerful calculator that ships with Windows

  • excalc

    vestris inc. expression calculator, circa 96'

    PSA: Here's another, much more feature-rich calculator called Expression Calculator (or Global Calculator sold in Germany in 1997), written in Delphi -, full source code and a working executable that still runs on any version of Windows.

  • Scout APM

    Less time debugging, more time building. Scout APM allows you to find and fix performance issues with no hassle. Now with error monitoring and external services monitoring, Scout is a developer's best friend when it comes to application development.

  • libqalculate

    Qalculate! library and CLI

    Check out Qalculate![1] for an application for a program that does what you specify and much more (though obviously not as much as WA).


  • calculator-specs

    Spec repository for Windows Calculator (

    It works like you say in standard mode by design because it's trying to match the behavior of older desk calculators that worked that way. In scientific mode it respects order of operations.

    There's a proposal to change the UI to make this clearer:

NOTE: The number of mentions on this list indicates mentions on common posts plus user suggested alternatives. Hence, a higher number means a more popular project.

Suggest a related project

Related posts