GS-Calc *.gsc files are typically several times smaller than equivalent ODF files. Thanks to specialized compression techniques, the difference can reach hundreds of times or more. Loading and saving operations can also be tens of times faster.

GS-Calc *.gsc files can be very large — they may exceed 4 GB. The only practical limit is that a single worksheet may use up to ~500 GB of RAM when loaded.

GS-Calc files are plain ZIP archives containing several streams: workbook data, images, file lists (with optional encryption), version metadata, and a thumbnail image stored at Thumbnail/thumbnails.png.

If the file is encrypted, both workbook data and all images are encrypted.

To associate the *.gsc file type with GS-Calc in Windows, run GS-Calc as an administrator and use:
Settings > Register GS-Calc *.gsc File Type

To remove the association, use:
Settings > Unregister GS-Calc *.gsc File Type

GS-Calc uses the Open Document Format (ODF) 1.2/1.3 specification, a standard used by several major applications.

Some GS-Calc–specific features cannot be saved in ODF files. When saving, GS-Calc checks which features will be omitted and displays a summary.

Before saving an *.ods file, you can choose whether it should be compatible with Google Sheets or Excel. This is important because dozens of Excel formulas are saved/loaded differently in Google Sheets.

Common differences include:

• GS-Calc requires array strings to be constant, e.g.:

  =SPARKLINE(D17,{"charttype","column";"ymin",0;"ymax",2000;"firstcolor","#334960"})

  Google Sheets allows embedded references:

  =SPARKLINE(D17,{"charttype","column";"ymin",0;"ymax",MAX(D17:E17);"firstcolor","#334960"})

  To address this, you may:

  • enter constant values,
  • use a sheet range reference (e.g., =SPARKLINE(D17,F1:G4)),
  • use VSTACK() or HSTACK() to build arrays dynamically.

• Google Sheets omits the attributes table:number-matrix-columns-spanned and table:number-matrix-rows-spanned for formulas returning arrays/matrices.

  After opening such files in GS-Calc (e.g., the last sheet of the “Annual Budget” template), you must:

  • update the sheet (F9),
  • delete all cells in the spilled area showing #FILL errors,

  so GS-Calc can recreate the spilled cells correctly.