40GB is not large enough. 80GB you can get by with but I would recommend 120 as a minimum. Even then you need to mange your usage and keep the drive clean of accumulated temp and junk files.

How many GB should Windows 10 take up?

Microsoft has raised Windows 10’s minimum storage requirement to 32 GB. Previously, it was either 16 GB or 20 GB. This change affects Windows 10’s upcoming May 2019 Update, also known as version 1903 or 19H1.

Is 50GB enough for Windows 10?

50GB is fine, Windows 10 Pro install for me was around 25GB I think. Home versions will be slightly less. Yes , but after installing programs like chrome , updates and other stuff , it might not be enough . … You will not have much space for your files or other programs.