On my system, 305GB. 810GB if I left my iTunes library on my boot drive (more on that below).
Most people do not take account that Applications should remain on your boot drive and quite a few will not run properly if installed anywhere else.
Although it is possible to pare my requirements down to a 1TB boot drive, it would take up too much time for me to swap my active work files in and out to externals. Life's too short.
2TB on board is my sweet spot between time spent on housekeeping and the huge cost of going to 4TB on my iMac Pro. I can do this only by taking advantage of the ability to offload my iTunes (500GB) onto an external in Mojave.
Offloading iTunes is possible in earlier Mac OS using Symbolic Links. Not as easy as in Mojave but the results are the same:
https://www.howtogeek.com/297721/how-to-create-and-use-symbolic-links-aka-symlinks-on-a-mac/
If this makes it easier for you to save money with a 256GB, then that's ok, too.
Many of the armchair experts around here will immediately tell you to get the 512GB system. That's not wrong when you're considering a 256 but they're not right either when no one really knows your needs—including me.
None of us are you. Do more research. Ask more questions if you must but tell us about yourself, how you use a computer, what apps you run now and what you'd really want a new iMac to do with you at the helm.
My OS and system areas running Mojave are currently using ~35 GB.
That sum includes all content under:
/Library
/opt
/System
/private
/usr
- and the remaining hidden folders.
- it also includes the approximate amount of the /Applications folder that is taken up by macOS applications.
Keep in mind that as applications are installed, cloud services used, etc. the system space usage will increase. For instance, I have ~2.5 GB of iCloud Notes taking up space within the number I quoted above. Applications will have libraries within that space that will also have varied usage, that are hard to accurately.
One of the biggest variables will be if you are using Time Machine which creates and stores snapshots in your system area. When I was using time machine, it was common for me to have ~20 GB of space for those snapshots on my drive. I've read posts here where people have much more than that used by snapshots.
i've got 250GB on my 12" macbook. applications folder is 7.5GB, and the combined OS/library is just under 11GB.
you'll be ok if you're not doing video or pro audio work, and your pictures (and music library) are manageable... (my itunes is 19GB, photos is 6GB). so, right now i have 121GB available.
really depends on what you're going to do with the imac. and, of course, you can always get an external drive to store work, old work, etc.
Offloading iTunes is possible in earlier Mac OS using Symbolic Links. Not as easy as in Mojave but the results are the same:
https://www.howtogeek.com/297721/how-to-create-and-use-symbolic-links-aka-symlinks-on-a-mac/
No need to use symlinks at all. If you hold down the option key when starting iTunes, you can choose to put the iTunes library wherever you want.
A new Mac out of the box will use abut 20GB of drive space for the OS and included free apps.Looking to get the 256 gb ssd iMac... I was wondering how much space is there standard taking into count the mounting of the disc and the OS?
Thanks!