For WoW, a good rule is to keep at least 70GB free on your C: drive , and 100GB+ free is safer if Windows updates and Battle.net are on the same disk.

Practical target

  • Minimum to avoid problems: about 70GB free.
  • Better buffer: 100GB or more.
  • Extra-safe if your SSD is small: try to keep roughly 15% to 20% free overall.

Why this matters

WoW updates can temporarily need a lot of extra working space, and Battle.net/Windows can also use the C: drive even if the game is installed elsewhere. If the drive gets too full, you can get update failures, stuttering, or crashes during patching.

Simple rule of thumb

If your C: drive is the Windows drive, don’t let it dip below 70GB free for WoW, and aim for 100GB+ if you want fewer headaches.

TL;DR

70GB free is the floor, 100GB+ is the comfortable zone.