PC REQUIREMENT:

Minimum:
Supported OS - Windows 7 SP1, Windows 8/8.1 (64-bit versions only)
Processor - Intel Core i5-750 @ 2.6 GHz or AMD Phenom II X4 955 @ 3.2 GHz
Memory - 4GB
Video Card - NVIDIA GeForce GTX 460 or AMD Radeon HD5850 (1 GB VRAM)
Direct X - Version 11
Hard Drive - 30 GB available space
Sound Card - DirectX 9.0c compatible sound card with latest drivers


Optimal:
Supported OS - MS Windows 7 SP1, MS Windows 8/8.1 (64-bit versions only)
Processor - Intel Core i5-2400S @ 2.5 GHz or AMD FX-8350 @ 4.0 GHz or better
Memory - 8 GB
Video Card - NVIDIA GeForce GTX 680 or AMD Radeon R9 290X or better (2 GB VRAM)
Direct X - Version 11
Hard Drive - 30 GB available space
Sound Card - DirectX 9.0c compatible sound card with latest drivers



SOURCE: http://blog.ubi.com/far-cry-4-pc-specs/