I've been told its the width that matters...

Anyhows, on a more serious note, you would need to use one of the user scripts for such a thing - gogrepo, adaliafundamentals or such like. Never used them myself. I wonder why the request though, even if you do acurately work it out, your unlikely to find a HDD exactly that size, and will grow, not too mention patches, docs etc. all change over time. Me, I just buy the biggest drive I can afford two (at least) of and one mirrors the other.

gogrepo.py was already mentioned, at least that gives you quite exact number when you run the gogrepo.py download -dryrun. It is especially good because you can define what exactly you'd want to download:

- which language versions, e.g. all that are available, or only English?
- Windows, Linux and/or Mac versions?
- Do you want to download the extras too?

For comparison: with 1353 games, I'm already past the 2 terabyte limit (only English Windows versions, with extras included). Not sure how much more it would be if I'd want to download all language versions and Linux+Mac too.

MaGog will, indeed, let you import your library, and by default shows a tally at the bottom of each results page of the total size of all listed games' installers. I don't know how accurate this total is, but it should at least give you a ballpark idea of how much space you might need, even if you might not want to rely on the estimate too heavily.

It's not about the size OR width of your collection, it's all about how you use it.

A huge collection is pointless and unsatisfying if you don't know what to do with it.

Isn't it more about the hardware you use it with?

Sadly, it doesn't matter how much space they take up because the immutable law of hard disk storage reigns supreme. For those that do not know it, the law states that "Your data will expand to become larger than the available storage." more or less. So if you know you don't have enough space then it doesn't matter what the total is, because you need more space anyway, but if you aren't sure if you have enough space then you don't have enough sapce and need more space anyway. Lastly, if you don't know how much space they take up and you do know that you have enough space, well... you're wrong - you need more space.

TL;DR version: You need to buy a new hard disk no matter what so don't skirt around it, just buy a new drive. Oh, and after you buy it remember - you still don't have enough space because of the law... :)

So sayeth the wise Alaundo.

Not really, as your collection really depends on which platforms and language versions you consider worth downloading, not to mention extras.

Of course if you download everything, I guess some scripts could give you an indication at least.

The problem with downloading everything is that there are patches which update certain previous versions to latest version and if you download the latest installers, then those patches are unneeded and eat up disk space which really could be saved simply by not downloading them.

Yes gogrepo does that, and I wouldn't be surprised lgogdownloader does too (I haven't used the latter).

gogrepo gives the exact amount of data still left to download (which depends on which language versions, OS versions etc. you intend to download, it calculates it in the beginning before starting to download), so either start the download and stop it with Ctrl-C right away (just so that you see that number), or I think there is also the -dryrun option so that it only simulates the download process, also giving you that number I think.

But first you need to set up gogrepo (install python 3 and some other dependencies from within python), run gogrepo update (which can take a long time, even several hours depending on the size of your library)... and only after that you can run the download command.