As per Microsoft, if you are able to use Windows 8.1, you are ready for the upgrade.
For those who still want the system requirements, read below:
Processor: 1 gigahertz (GHz) or faster
RAM: 1 gigabyte (GB) (32-bit) or 2 GB (64-bit)
Free hard disk space: 16 GB
Graphics card: Microsoft DirectX 9 graphics device with WDDM driver
A Microsoft account and Internet access.
