This is the best simple guideline: https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/10/html/managing_storage_devices/getting-started-with-swap#recommended-system-swap-space

Basically, if you want your system to be able to hibernate then you need enough swap space to sustain both the active swap file and a full image of the live system RAM (hibernate = suspend-to-disk, and uses the swap space). The swap file could be as large as the RAM, so a safe value is 2x the RAM. If you don't want to dedicate that much disk space to swap, the safe option is to disable hibernation but note that suspend-to-disk is safer for system recovery in the event of power failure.

If you've ever had a Linux system go into hibernate and fail to awake, lack of swap space was probably the reason.

In Red Hat's chart where they recommend 1.5x RAM for 8-64 GiB, basically you're hoping that your system is never completely using all of the RAM. If you do cap out the RAM such that the swap file plus the in-use memory is greater than 1.5x RAM, and the system goes into hibernate, it will not recover because there isn't enough free swap space to store the in-use memory. You have to make a judgment call when you set up your system about how you're going to use it - whether you expect to be using 100% of the RAM at any point, whether you'll remember to close some running applications to free up memory every time you leave the system idle long enough to go into hibernate, whether other users will be using the system (if they're logged in then they are partially using the RAM and the swap), etc.

Deciding how much swap space you need is a risk management decision based on your tolerance for data loss, application stability, and whether or not you need hibernation.

What I'd recommend is setting up a few testing systems with 2-3GB of swap or more, and monitoring what happens over the course of a week or so under varying (memory) load conditions. As long as you haven't encountered severe memory starvation during that week – in which case the test will not have been very useful – you will probably end up with some number of MB of swap occupied.

And

[... On Linux Kernel > 4.0] having a swap size of a few GB keeps your options open on modern kernels.

And finally

For laptop/desktop users who want to hibernate to swap, this also needs to be taken into account – in this case your swap file should be at least your physical RAM size.

I like zram! It has pretty low overhead and usually compresses data quite well (~2/3x). I have it set to the size of my total ram and I can't notice when it starts to kick in.

Some small amount of swap is also nice to have, but it gets rarely used for me, because zram gets used first.

One trick that might be useful is that you can create a normal swap file and enable swap to it in cases where you want more. For example recently I needed to load 64GB of data on a 32GB laptop, so I created a 64GB swap file on the filesystem and used swapon to enable it. (just disable it before hybernation if you use it!)

It just takes a bit longer to run, but if you don't need all the data loaded at once it's much faster than moving the code on a more powerful pc (or fixing it)...