How much space does Windows 10 use? I want an SSD for the OS and maybe 5 games and I am wondering the size I should get, I am on a tight budget.
Win10 takes about 20GB of disk space.
Windows 10 on my machine is about 20 gb for 64 bit version of the OS. However please remember you will need extra space if you want to allow your pc to hibernate (which can be more equal to the size of your ram, i.e. 16 gb for most people), plus space for swap file/page file, which can easily be 10+ gb or more depending on your system. So...just for "OS", I would recommend at least about 50 gb - not including any other programs you want to install.
Depending how much space your games and other software take, might be more economical to get a larger 3-4 tb hdd if you dont have plans to get one yet. A lot of triple AAA titles now take up 40-70 GB already, and future games will take up even more space.
I will get a 60gb ssd for now (I have 8GB RAM) and get another 256GB one in the future. On the 60GB one I will put OS and a few games (Rocket League, Cobalt, Split Second). I will be running the SSD along a 1TB HDD.