A comment I saw recently suggested that 7 to 9 in a party is "too big", and I gotta admit I nearly fell outta my chair laughing.

When I run a campaign in my group, if the campaign has gotten interest, I can have over 20 people in a group.  Normally, I break it up into three groups, and the average party size is 8. 

I am used to running large, complex stuff like that, however, and I am aware that I can be something of an outlier, so I thought I would simply hop in and ask folks what they thought of as "too big" and "too large".

My last campaign I had 24 people start the final boss fight, all of them knowing that they were gonna die (major foreshadowing plus really tough baddie and lotsa player driven reasons for sacrifice, blah blah). 

I am aware that folks have lots of worries about combat taking so much time with large groups -- we have our own ways of handling that and a five round combat usually takes less than 30 minutes in my 8 person sized groups.

SO, what is too large a party (an be aware there are no wrong answers here, because it is really all about the DM's ability to handle it).

Six is the upper limit for me. Not because it is hard to manage but because it slows way down when there are that many voices at the table. Combat becomes a slog too when it gets to be over six.

The group I play with has 9 total (1 DM + 8 players) and we've decided that's the limit we want.  When everyone can make a session we can have some really epic encounters.  If someone can't make a session, we can still get stuff accomplished without feeling hindered by a lack of players.

I agree that combat can slow down with a larger group.  We use a visible tracker and the DM will go through the initiative order and call out who the next 2 in line are so people know they need to start thinking about what they are going to do.  That helps out a ton.

The largest party I have ever played in to date was 7 players, so 8 with the DM included.

The Combat was a bit slow, but to help it keep moving, the players near the player that is to go next would help them decide on their next course of action, and we burned through a complex One-Shot and everyone had a blast.

Personally I think that I would start to consider a party to be 'bug' at 10, but am not sure of what 'too big' would look like.

D&D fifth edition is designed around party's of 4-6 players and I've got to agree with that as my sweet spot, although I'm very happy with just 3 players. It's not so much complexity but the fact that above say 5 players, you're looking at a lot of downtime per player as things naturally cycle. The biggest party I've run is 7 and it was just tedious for everyone.

As a note, two of the tricks I use to speed up combat may or may not be useful to others, but we have often known each other for a very long time and so are comfortable doing them.

The first trick is that I give folks 10 seconds to describe what they do on their turn. When we first started, we really made it a firm rule, but now it is a little more flexible because we don't have the decision paralysis (the um, ah, err). after long practice. With this I note that like the above comment, everyone knows when their turn is coming up -- and I do allow them to be 'skipped", but when I do, it means they don't take an action that turn (consequences).

The second trick is pre-rolling. Because folks know their turn is coming up, lol, and the goal is to know what you are going to do, you make the roll. On your turn is when the calculations and the DM rolls happen. If there is a point where disadvantage cancels out advantage, the player gets the higher roll anyway (they are the heroes, after all).

Edit: I have been told I need to point out that I more often do a quick bit of math in my head and take the average of the two dice if they rolled presuming advantage and it was canceled out. There, are you happy now?
It is true -- I do that. 

I prefer to run four, will flex to five or six for the right reasons... but to the greater question I have run campaigns for a dozen or so people all at once, as well as "raids" for 20+ people.

I like small tables because it's fast. Every tip that makes large groups faster also makes small groups faster. That speed gives combat energy and helps people like me stay focused.

That said, it all depends on what the story needs at any given point in time.

This is the way I handle group sizes; the key is adjusting the tone of the game to accommodate.  

2 (with a sidekick each)- 3 players: The Roleplay/backstory heavy group.  With this few of players, we have plenty of time for all this.  

4-5 players: The balanced group.  With this size of group we can have a balanced mix of combat, dungeons, and a side of roleplay. 

6-7 players: The dungeon crawl group: When the group is this large the players need to understand that dungeon crawling and combat will be the focus, and they can’t derail that.  The meat grinder group.  

8+ players: too large, not recommended. 

Depends on the skill of the DM I have played in a group of 14 way back in the day running Castle Greyhawk  combat was kind slow but if we needed snacks people could run and get stuff.  Six players  is my limit

 3-5 players is the answer.

I personally aim for four or five.  With three, you end up in situations where folks are likely to settle into two-versus-one whenever there is a decision, limiting their discussion of their options (and some of the roleplay fun that comes with it).  With six, combat starts to get a bit wonky—that is a lot of downtime between individuals taking their turn, so eyes might start to glaze over, which only compounds the problem of folks not being prepared for their turn. Out of combat, it often stretches out gameplay as there are more people weighing in or being responded to, leading, at best, to long correspondence for simple decisions and, at worst, to decision paralysis. 

I will run six if that is how things shake out - perhaps someone in a group of five has family in town and they want to give D&D a shot as a guest character. I’ll also run three if someone in a group of four is not able to show up. But above of below that is not overly enjoyable for me to DM for, and it doesn’t tend to be enjoyable for the folks I play with.  Outside of extenuating circumstances, I am sticking to five as my soft cap and six as a hard cap.

Honestly it depends on the DM and players. 

If you've got an experienced DM with a group of players who know what they're doing and plan their moves in advance, then even up to 8 works. Critical role often works with 8 players. Meanwhile If you've got a new DM who is having to look up every other rule, and players who take 20 mins each for their turn at level 2, then even 3 players can feel unwieldly. 

Personally I like a DM+5 players. It ensures the game still runs well even with a full party, while a player or two can drop out for irl reasons without preventing the session from running.

4 players in general and up to 6 if they all are really experienced and attentive, with a 1 minute rule on their turn in combat. Everything above gets cumbersome.

Quote from Erik_Soong >>

Six is the upper limit for me. Not because it is hard to manage but because it slows way down when there are that many voices at the table. Combat becomes a slog too when it gets to be over six.

Same. I tried running one of the Keys From the Golden Vault adventures briefly at school and had 8 people. It was a disaster.

Everyone was splitting up, and I had to constantly cut from person to person so that everyone could get a turn. People were just playing video games during part of it because there were portions of the game where they were doing nothing.

Now, I definitely could have done things better and the fact that the party split up was what spelled doom. However, generally, running for a group with 8 people is nowhere near as fun for anyone involved just because people get less time for individual roleplay or character development, and combat takes a billion times longer.

Obviously, there are ways and campaign designs to manage this somewhat. And if the OP is able to handle and have fun running groups of 8, then kudos to them. Ultimately though, every time someone other than AEDorsay has had a group as large as this, I've only seen it mentioned because it was one of the main factors making their DMing job way more difficult and stressful.

Quote from Erik_Soong >>

Six is the upper limit for me. Not because it is hard to manage but because it slows way down when there are that many voices at the table. Combat becomes a slog too when it gets to be over six.

 This.

As a rough guide, DM along with set up time, breaks etc take up 50% of the time. That means in a 3 hour session (which is what I get to typically play), there's an hour and a half to divvy up between the players. Three hours, and I get to talk for about 11 minutes...and that's assuming I get my fair share. Worse, with that many people, there's a lot more discussion about what to do, persuasion to follow a plan, etc etc. That will seriously eat into what time each player has...and is of little interest to me. Philosophising, sure, but debating whether we should sneak in or use a distraction? I'd rather minimise that time. 

The problems that come with large parties have little to do with the DM. Sure, a poor DM might struggle more than a good one...but the problems are inherent to having large parties. Less time per player to actually play, and more wastage as everyone tries to move forward as a group. Combats, already an issue with 5e, start ballooning. They also become constrained - swarm combats can be fun with four PCs, but become incredibly bloated when balanced for eight, for example. Interactions become more shallow, as relationships multiply. It's just how numbers work.

If I booked to go on a session and there were 10 people at the table, I'd walk back out again. I find that 4 or 5 is ideal. Enough complexity to have interesting and unpredicted results...but not so many that they start tripping each other up. One either side and it isn't too detrimental. Going further and the quality starts to suffer.

As the thread shows, under standard 5e, a group of 4-6 is about the max group size before things truly begin to bog down.  As well, keeping track of more than that stars turning into a headache, too.  Not much doubt, 3-4 is pretty close to "ideal" with a decent balance of enough players to have a decent group dynamic and power and few enough to really have things flow well.

It's important to note that OP (who has/had, 20+ players) homebrews a TON.  I see their posts in a lot of areas and they have homebrewed a truckload of things, from rules, to classes to ability scores and more.  I personally think that's awesome, to be able to take the baseline, twist and tweak it to fit your dynamic and end up with something that you and your group enjoy at 100% + a bit of what vanilla 5e offers.  It's also important to realize that with that level of customization, few, if any of us, are thinking of and working with a system similar to what OP is running.  Kind of like comparing apples from the tree to a 5 course gourmet meal.

Quote from Falwith >>

It's also important to realize that with that level of customization, few, if any of us, are thinking of and working with a system similar to what OP is running.  Kind of like comparing apples from the tree to a 5 course gourmet meal.

 
Thank you for the compliments!

I should note that what we've done is take all of 5e and simply make it "more" of what we needed out of it. So, like, 90% of what I have brewed and distilled in my wee workshop is mostly tack ons, lol.  The sort that can make for longer combats and such if everyone isn't familiar with them, and the kind that means a little more resource control because we tend to be crunchier that way.

Maybe less than 90, since folks think of class and race as big things, but we've been doing that kind of stuff for decades. The most dramatic change we've done is also the most recent, and that's the change to magic so that it has sound rules, works on points, and gets stronger as the caster does. That's a big one.

But we use all the same spells, all the same monsters, all the same special abilities.  Ain't gonna re-invent the wheel, just add spokes, lol.

My main group is between 10-14 players depending on the week.  It's super chaotic outside combat, and each player only gets 1-2 turns in combat due to how many people there are, but it can still work fine

2 is way too few. 3 is ok. 4 is propably better. 5 is way too many. 

Might I suggest that just because it's fun for the DM and players are turning up and having some enjoyment...perhaps that doesn't mean it's anything close to optimal for players?

I have a question.

Perhaps this is an opportunity to ask a related question that might help shed light on this...

How long on average does it take for a player at your table to complete a turn during combat? I don't mean mentally evaluate how long you think it should take, I mean work out how long a combat takes to run, divide it by the number of rounds and then divide that by the number of players (including the DM).