How to determine system requirements for my game?

[smguyk]

Hard drive space is easy to determine. For RAM usage I use the task manager which in my experience has good enough accuracy.

But what about CPU requirements? And GPU? Is the graphics card even used by my game? What about the sound card etc.?

Obviously I could let other people test the game or use different machines, but is there another way that I can use myself to get a rough estimate on what is required for the game to run?

So basically I need info about this stuff (minimum requirements):

OS, processor, drive space, RAM, sound card, directx/opengl version, graphics

[Jesper Juhl]

For CPU requirements I'd say yo have to go test on some old machines and see how they perform. Or just make a handwaving guess based on how it performs on your machine.
As for GPU. Well, you can start by determining the minimum OpenGL version your game requires - any graphics card that can't provide that is clearly not supported. Beyond that; test with some older cards or guestimate based on the hardware you already have.
GPU RAM requirements should be fairly easy to estimate based on the textures you load (remember to count their raw uncompressed size - a 100KB PNG image will take up more than that once uncompressed and placed in VRAM).
OS is easy. What Operating Systems have you implemented the game on/tested with? Linux? OS X? Win Vista? Win 10? Should be easy to come up with a list.

[GraphicsWhale]

If your game is trivial, there's no real reason to specific system requirements aside from operating system.

- OS
How do you not know how to determine this? If you compile and run a build on your platform, that means that the output is for your platform. So if I build a program with MSVC on Windows, and it outputs EXEs, and I can run them, it's obvious in multiple ways that I am in fact creating binaries for Windows.

- Graphics card
In terms of driver support, if you're using SFML's graphics module, I might be wrong, but I believe it requires OpenGL 2.1 or newer. If you're using OpenGL directly, you should know what version you're using, in which case that's what's required.

In terms of performance, If you can, test it out on some really other computers and see how well it works with them (if you can, determine their specifications and how they compare in terms of raw performance compared to other computers tested, which may give you a better idea of just how much performance your game demands).

- CPU
Much harder to measure. It's not as simple as "2ghz or more" because there can be a huge performance gap between two processors at the same speed with the same amount of cores. Plus, things like RAM speed, cache, and even background applications running on the computer can have an impact.

While you can use a virtual machine to test this to some extent, I recommend just testing it out of various computers, see how much performance it takes up (look at task manager or something), and giving a generously-high requirement.

- RAM
Track your allocations, look at task manager, etc. It's pretty easy to determine how much RAM your game takes up. But keep in mind that you're suggesting the amount of RAM their whole system should have at a minimum for playing your game, so suggest just that and not the amount of RAM your game uses (such as if your game uses 80mb RAM, say you need at least 1GB, or if your game takes 2GB, say you need 4GB).

- Storage Space
You're generally just suggesting how much free space they should have for the game, not how big their drives should be. Just take the size of your game (including all the assets) and add a bit more for any files the game may create (such as save files).

- Sound Card
I don't know what SFML uses or what it's compatible with, but I'm fairly certain that this isn't any serious compatibility issue for most computers.