The minimum amount of RAM needed for Last Days of Humanity is 8GB. However, you should consider upgrading your RAM to 16GB or more if you plan to play online with your friends. Consider 32GB or more for a public server to support many people playing at the same time. Remember, Last Days of Humanity packs a few graphic-enhancing mods, also known as shaders, and they require quite a lot of processing power to be able to play smoothly and handle chunk loading easily.