Here's the specs from windows.com:
If you want to upgrade to Windows 10 on your PC or tablet, here’s what it takes.
Latest OS: Make sure you are running the latest version either Windows 7 SP1 or Windows 8.1 Update.
Don’t know which version you are running? Check here to find out.
Need to download the latest version? Click here for Windows 7 SP1 or Windows 8.1 Update.
Processor: 1 gigahertz (GHz) or faster processor or SoC
RAM: 1 gigabyte (GB) for 32-bit or 2 GB for 64-bit
Hard disk space: 16 GB for 32-bit OS 20 GB for 64-bit OS
Graphics card: DirectX 9 or later with WDDM 1.0 driver
Display: 1024x600