According to Ubisoft, you'll need a serious PC system even for 1080p resolution, let alone a 4K one. The game will have an integrated benchmark and a couple of different presets but still it will need at least 8GB as a standard and some serious graphics card power to run at all.
The minimum requirements, which use low video preset and target 720p resolution include Intel Core i5-2400 or AMD FX-6300 CPU, Nvidia GTX 670 or AMD R9 270 with 2GB of VRAM and the aforementioned 8GB of RAM. The recommended requirements, which aims at 1080p gaming with high video preset, starts with Intel Core i7-4700 or AMD Ryzen 5 1600, Nvidia GTX 970 or AMD R9 290X with 4GB of VRAM and the same 8GB of RAM.
The 4K at 30fps requirements include Core i7-6700 or Ryzen 5 1600X, GTX 1070 or RX Vega 56 with 8GB of VRAM and 16GB of RAM. The 4K at 60fps requirements raises the bar to Core i7-6700K or Ryzen 7 1700X and Nvidia GTX 1080 SLI or two RX Vega 56 in Crossfire. Bear in mind that the 4K at 60fps also lists video preset as high/ultra while the 4k at 30fps sticks with high video preset.
The 4K also suggests Windows 10 OS, while minimum and recommended settings also list Windows 7 and Windows 8.1. Bear in mind that these are only 64-bit versions.
Although we didn't doubt it, Ubisoft has also listed plenty of supported graphics cards which include Nvidia GTX 600, 700, 900 and GTX 10-series graphics cards while from AMD side, it supports Radeon 200, 300/Fury X, 400 and Radeon Vega series. Some entry-level graphics cards are excluded for obvious reasons.
Since the game looks really impressive, the rather high system requirements are not much of a surprise. It is also interesting to see that RX Vega 56 is in line with the GTX 1080, suggesting that Ubisoft made sure that the game is well optimized for AMD Vega graphics cards.
As noted, the Far Cry 5 will officially launch on March 27th on PC, Xbox One and Playstation 4.