This is the source code for computing the seasonal fractional snow-covered area. It is written in Fortran 90. The code reads snow depth (HS) and snow water equivalent (SWE) data from the provided example file HS_SWE.txt and writes the computed fractional snow-covered area (fSCA) to a file fSCA.txt. The current version can be found in the WSL/SLF Gitlab repository: https://gitlabext.wsl.ch/snow-models/fractional-snow-covered-area