hmm. I thought he was asking about WINDOWs fitting. But while we're on the topic of Linux fitting, here's my Linux DF for / and /home:
/dev/sda2 37G 26G 9.6G 73% /
/dev/sdb2 1.8T 1.7T 18G 99% /home
So, ignoring home, my laptop Linux Mint fits fine in 30G. And I've got LOTS of 'junk' loaded. At my last job, I allocated around 30G for the Linux partition, if I remember right, which was pretty much a default install of Linux Mint.
That being said, here are some sizes for the virtual PCs I've created for the class I teach:
Ubuntu2.2: 28.92 GB
Ubuntu2.2: 25.85 GB.
MicroOS: 34.46GB
EdUbuntu: 24.0GB
CentOS: 30.15GB
Note that these were 'mostly' 'standard' installs, but obviously YMMV! (especially since MY mileage varied!)
Now, I also did a Windows install, W11 or W10 I think, and I don't think I added much to it, and it took 50.0GB
So, for Windows I agree that you're probably out of luck getting it in to 30GB! ;-)