Technologies are described herein for the automated offloading of the execution of a user-defined function (“UDF”) to a high performance computing (“HPC”) system. When a request is received to calculate a workbook that references a UDF, a spreadsheet application program determines, based upon a tag set by the UDF, whether the UDF is safe for execution on the HPC system. If the UDF is safe for execution on the HPC system, the spreadsheet application program causes the UDF to be executed on the HPC system using a connector that communicates with the HPC system to cause the UDF to be executed thereupon. A container executing on the HPC system emulates interfaces provided by the spreadsheet application program and is utilized to execute the UDF. Results of the execution of the UDF on the HPC system may be returned asynchronously to the connector and to the spreadsheet application program.