How long can I estimate a combat to take, and how long should an average dungeon be?

Question

Upon going back and looking at the dungeons I've created in the past, many of them have lasted for too long. I want to create a feeling of scope and adversity, and I don't want it to feel like a slog for the players. I understand combats tend to get longer as more spells and options open up for both the players and monsters, but I can find ways to shorten an encounter through other questions. My question today is, how long can I estimate a fight to take, based on whether it's Easy, Average, Challenging, Hard, or Epic, and how long should the average dungeon be, in terms of combats? The answer to the first question should help me to find the second question.

And for what specifically I mean by the difficulty levels:

Easy CR-1

Average CR +0

Challenging CR +1

Hard CR +2

Epic CR +3

Answer 1

It depends

It heavily depends on the number of players and enemies (a CR +0 encounter for 4 characters takes significantly less than a CR +0 encounter for a party of 8, and a CR +0 encounter for the same party could be composed of many weaker monsters or a single boss), on the availability of save-or-die spells and whether they land or not, on the complexity of rules involved in your PCs and NPCs (sometimes, finding the rules to grapple in D&D 3.5 greatly slowed the game. I'm pretty sure there are equivalent situations in Pathfinder too), on the players being attentive or not and, on the increasing number of options for high level monsters and PCs and, in general, on lots of independent factors that's impossible to predict in advance.

(I had gaming sessions with 5 encounters easily solved in the same 3-hour game night and in the following encounter the same time was used to play the first turn and a half of a combat, just because of a silence spell forcing the casters to be creative.)

I've come to the conclusion it's downright impossible to pre-determine the duration of an encounter before playing it, unless you fiddle with monster's HP on the run, having your enemies last longer or die faster as needed... which is probably not the game experience you were looking for and feels a little like cheating them to me, not letting their expertise or luck shorten an encounter and ultimately preventing theem from actually influencing the outputs of (that part of) your narration.

However, I feel there still is something you can do to prevent that feeling of sloppiness.
Have your encounters be meaningful. No more filler encounters, random goblins in a side-room. If you don't want to skip that room because it makes sense in the dungeon, consider having the monsters in there really weak and skip the actual combato, or even better offer your players to spend some resources ("...You lose 30 hp and 3 levels of spells and you win. Is this ok or do you want to play it?")

This means shorter dungeons and less time spent in useless goblin-mashing, which should make dungeons more interesting.
On this page, the dungeon's lenght should be tied to what the dungeon is in the game world (are they exploring some dwarven mines? That could be huge) but if you want to go for a less realistic but more gamey perspective, a dungeon should be clearable without going to rest. This usually means 4-6 encounters in my book, to be played over 2 or 3 gaming sessions. Your Mileage May Vary.
Another option is googling for some 5-room-dungeons. These are a series of 5 "rooms" (true, they are called dungeons, but the same structure is often used to describe any string of different places) following an identical structure:

• Room One: Entrance And Guardian
• Room Two: Puzzle Or Roleplaying Challenge
• Room Three: Trick or Setback
• Room Four: Climax, Big Battle Or Conflict
• Room Five: Reward, Revelation, Plot Twist

Five rooms, one to three combat encounters (in rooms 1, 3 and 4) feels like a popular choice.

Answer 2

To be quite frank, expect your Players to take far longer on the easy stuff and and breeze through the hard stuff when you least expect it.

On average, if it is not just a "murder everything that move" kill style campaign the groups Im with tend to have a max 3-4 average encounters in a 3-4hr session with RPing. Often this number is lower as the roleplaying aspect and gathering information are just as valuable as the monsters for build a world.

If its a hard or epic encounter we might have one or 2 average encounters or the whole night may be just the epic encounter. Any more than that in a 3-4 hr stretch and the other PCs tend to get fatigued (physically).

There is no hard and fast rule as to how fast time wise an encounter will take. Given 2 options, PCs will invariably create and take a third option. As a DM you should support and nurture that, and be prepared for the best laid plans of mice and men...have often been waylaid by something off the cuff.

Addendum: DO NOT GO ABOVE 4 battles in a normal situation. If the players dont recoup with RP or something other than battles they WILL get fatigued and less likely to want to go at the campaign in any rush. Unless luck is with them that night...in which case, make em feel heroic.

Answer 3

In my experience, difficulty (as measured by CR) doesn't have that much to do with how long an encounter takes. I generally expect any encounter to take about 45 minutes. Then, any of the following factors can add another 30 minutes or so:

• A PC comes very near death. Players take longer weighing all options.
• High (5+) player count
• High enemy count or complexity
• Complicated or unfamiliar rules resolutions (poison, any spell with 2+ paragraph description, combat maneuvers, etc)
• Disengagement resulting from any combination of the above (the longer combat takes, the longer combat takes)

So usually I expect an encounter to last a little over an hour on average. If many different factors combine into the perfect slog, an encounter can drag for almost two hours.