Short answer: 8GB
Longer answer:
Photoshop is a bit of a resource hog, and it can take advantage of a lot of RAM. The minimum amount of RAM that you can get away with is 8GB, but we recommend at least 16GB for photo editing. If you’re working with large files or doing a lot of multitasking, you may even need 32GB or more.
PRO TIP: If you are considering upgrading your RAM to run Photoshop, be aware that there is no one-size-fits-all answer. The amount of RAM you need depends on the size and complexity of the files you are working with, as well as the number of other applications you have running at the same time. As a general rule, 4GB of RAM should be enough for most users, but power users may need 8GB or more.
Photoshop is a resource-intensive program, so it benefits from having a lot of RAM. The minimum amount of RAM that you can get away with for running Photoshop is 8GB, but we recommend at least 16GB for photo editing.