How much RAM do I need?

This is a misleading question as it provides an answer to a question you never intended to ask. The question you’re trying to ask is “how much RAM do I need to run my server?”

The answer to the question “how much ram do I need for X amount of players?” is “player count doesn’t directly equate to more or less RAM usage”, which is much less helpful an answer than what you would get by simply asking “how much RAM would I need for this server that I want to create?”

Be careful about asking questions like this; they’re commonly referred to as XY problems and these types of questions won’t get you any closer to your goal and will, most of the time, lead you down rabbit holes filled with only pain and suffering.

You want to give your server enough RAM to avoid constant GC or garbage collection. If the JVM’s garbage collector is constantly running and trying to clear out space then you need to allocate more RAM. OOM (out of memory) errors do not necessarily mean you need to allocate more memory to your server as they can often be caused by poorly-developed plugins attempting to manage their own memory. This type of problem is usually a memory leak as opposed to a lack of allocated memory and is inefficiently (and rarely) solved by simply increasing the amount of memory.