A typical humanoid, in combat, tends to occupy a 5′ square. Whilst brandishing sharp &/or dangerous weapons this just makes sense. Rules change for squeeze situations, pending relationship(s) – be they friend, foe, romantic (thus both), necessity (neither) or ‘strictly business’. These ‘combat &/or squeeze’ rules are somewhat realistic, makes intuitive sense and work well for in-game rulings.
Contrast this with reality:
Real world humans do not tend to observe nor respect one another’s boundaries. See any concert, crowded elevator, zombie movies – or try to enforce social distancing in most retail locations – you will observe very different situations.
Why This Is Relevant To D&D & To ALL ‘Role-Playing’ Gaming:
Seven goblins in a snowfall, backed up to a tiny bluff. Whilst huddling up to a tiny fire they are hit by bon-firing / cantripping that hits a large number of them.
Whilst thirty-three zombies cluster-reach through a portcullis a large urn of oil (above) pours & splashes down and is set ablaze.
Three clumsy ogres slip-fall into a 10′ cube-pit and seek to angrily push-throw one another out.
A blue dragon (lightning: ‘long and narrow’) breathing on the crush of two phalanx groups clashing – how many are shocked?
What is squeezing? – this defines what is in the 5e rules on squeezing during combat, including more squishy shapes, oozes and such.
Can medium creatures squeeze into smaller spaces? – this rehashes the rules quite well, including what a squeeze does to combat tactics.
What minimal space can a creature go through whilst squeezing? – this one requests information how much space a single creature (usually medium humanoid) needs. This also seems to suggest that i will also not find an answer for this ‘how tight is a group’ question.
Question Repeated: What rules exist in any edition to tabulate density of crowded groups in tight, pressing, forced or out-of-combat situations?
Note to editor: I searched Stack Exchange and found the above three previous questions / if i have missed this please accept my apologies. Also, any ruling from any roleplaying book, even if not 5e, could be excellent – i am encouraging any answer at this time. A good answer might even be from people who run concerts, dances or any other crowded pre-COVID events that – any that manage flows of moving-standing persons. Any guide would help. I may have to repost this in a different section of Stack Exchange or even (shudder), Reddit.