What is an Custom Function?

Both Microsoft Excel and Google Sheets support Custom Functions, or user-defined functions. These functions extend the calculation and data-import capabilities of Microsoft Excel or Googel Spreadsheet. Developers create custom calculation packages to provide:

  • Functions that are not built into the applications.
  • Custom implementations to built-in functions.
  • Custom data feeds for legacy or unsupported data sources, and application-specific data flows.
Users who create workbooks can call Custom Functions from a cell through formulas—for example, "=MyFunction(A1*3.42)"—just like they call built-in functions.