I'm playing in a campaign, mostly RP, but when it comes to combat, we are horribly slow. For example, our first dungeon took three sessions. THREE SESSIONS! That's just way too much. So, anyone have some suggestions to speeding up combat?

I know someone who used a physical timer for something that was extremely critical - the players damaged a security system which is the only reason it didn't kill them all outright, but the damage was going to cause a massive catastrophe, killing a lot of people, if not stopped or evaded.

Another DM kept reminding the players that their characters didn't have enough time to discuss things so much during combat which is 6 seconds per round.

There's another TTRPG game played by that first group I mentioned where how much time they spend to complete a round affects "clocks" that the GM monitors - moving said "clocks" based on used time which count down until (usually undesired) events kick off. Time isn't strictly defined as 6s/round in that game, though. (EDIT: Clocks in that game don't measure just time. They also measure how many mistakes the players can make before some undesired consequence will happen. EDIT again: The GM mentions when "clocks" move to make sure the players know the urgency of getting things done quickly and usually quietly. In that game, mistakes can push time-based clocks forward, too... BUT, the players are figuring out ways to use that to their advantage - which is a good thing.)

Chapter 9 of the DMG offers some ways of modifying the rounds to affect the speed of play. Feel free to try out different things and see what works - your own ideas, too, not just what's written in the chapter.

30 Second Sand timer. If the GM flips, you spend your round doing nothing. Knowing your PC. Knowing your fellow pcs. Before or after sessions discuss tactics. Dibs. Highest DPR person takes on the big foe, everyone else takes on the minions. 

Quote from jasperrdm >>

30 Second Sand timer. If the GM flips, you spend your round doing nothing. Knowing your PC. Knowing your fellow pcs. Before or after sessions discuss tactics. Dibs. Highest DPR person takes on the big foe, everyone else takes on the minions. 

 We tried a timer. That didn't work. It was still really slow

With that second group I mentioned in my reply, the DM will sometimes interrupt the players spending way too much time planning something just before an imminent event kicks off by kicking off the event and whatever the players were doing or saying is included into the start of the event. This has led to some entertaining but awkward encounters where the players were trying to plan an elaborate ruse just before meeting someone and the person they're trying to fool walks in on their talking characters.

That same DM has twice used a gargantuan dragon construct to remind the players that they're taking too long for an RP event. (It appears on the table in front of the minis and flies off, and the players get the hint. It's about to become a running gag if it keeps up.)

I'd need more context to give advice... combat can go slow for a lot of reasons. Are the players taking a long time each round to decide what to do? Are they having long conversations discussing tactics? Or are there just a lot of pieces on the board? Either the adventure uses a lot of little enemies every combat or maybe you just have a particularly large group. Once you hit 5+ players, combat inevitably stretches far longer to accommodate. 

Are you giving each monster on the board a separate place in the initiative or letting them all go at once? When groups of enemies are getting hit with Saving Throw spells, are you rolling separately for each one or doing a blanket check for the group? Something else that can be done is skipping rolling damage for enemies... attacks on NPC sheets list average damage for attacks, and you can save yourself some time by just always dealing average damage instead of rolling each round.

We dont really know what it is making combat slow. I think it might be arguing over some rule or something, which some of us have a habit of doing.

There is no arguing rules at the table. You ask about it, the DM makes a ruling, you accept it. PERIOD.

You are allowed to say, "OK, I don't agree with that rule interpretation but let's go with it now and I'll talk with you about it later." But that's it. You are not allowed to argue at the table.

How many players are at the table and how many enemies were you fighting?

Quote from Bhuraelea >>

How many players are at the table and how many enemies were you fighting?

 We are 5 players, and we are playing LMoP, so it varmes how many enemies we’re fighting

Quote from BioWizard >>

There is no arguing rules at the table. You ask about it, the DM makes a ruling, you accept it. PERIOD.

You are allowed to say, "OK, I don't agree with that rule interpretation but let's go with it now and I'll talk with you about it later." But that's it. You are not allowed to argue at the table.

 We are trying to get better at that

As others say, it’s tough to say exactly without more explanation. One time saver can be to cut back on rolling and just use average damage (at least on the DM side, rolling is fun and I think most players prefer to roll for their damage). Or at least roll to hit and damage at the same time so if it hits, you’re ready to go. 

Are you a group with newer players and/or DM? That can really slow thing down, particularly in an rp heavy campaign where people aren’t familiar with the combat rules. Do the players know what their characters can do? In particular spellcasters can take a long time, where melee classes just run up and whack the bad guy with sharp metal objects. Casters can take forever if the player is trying to decide which spell, and needs to look up each spell to double check if they are picking the right one, and doesn’t remember if they make an attack or the enemy makes a save, and they don’t know their save DC, etc.

Are there expanded out of combat discussions? Deciding to short rest or not, or turn right or left, or planning strategy because you know there’s a room full of goblins just ahead. That can make the dungeon take a long time without combat actually being the culprit  

Also, how long are your sessions? Three might be reasonable if you’re only playing for 1-2 hours at a time, depending on the size of the dungeon. 

Also 3 sessions to get through a dungeon is not necessarily too much. Depends on the dungeon size. If it's 10 rooms or something, that'd be 3-4 rooms a session. In a 3 hour session, that would probably not be that slow.

I have the same problem! I usually get through one encounter a session, sometimes 2. my encounters (not just combat) take my players waaaay tool long! and I have no idea why. we don't have rule discussions, tactics discussions, anything like that very often, slowing the game.

Some solutions I can think of:

—Are people using phones/computers at the table? When people aren't paying attention, combat tends to drag out A LOT longer. Making sure everyone is present at the table not only makes the game more fun, but it speeds up combat massively! People should use the time before their turn to decide what to do on their turn, not waste their turn thinking.

—Are you strategizing between turns? As a DM, I hate this. It slows play down to a crawl, and it's unrealistic that your characters would know how to coordinate unless they discussed tactics beforehand. I usually shut down out-of-character tactical discussions in combat, it's essentially metagaming.

—Are there a lot of new players playing casters? My rule with magic classes is, at this point, "if you need to read your spell for more than ten seconds to know what it does, you shouldn't be casting it." It's hard to fix this when you've already started, but printing some spell cards and bolding the most important info could hugely cut down on reference time.

These are all problems that I've encountered in my own groups over the years, and I think they're fairly common. They're fairly easy to fix, but it'll take some buy-in from your fellow players!

Edit: yeah, for the first LMOP dungeon, the goblin cave, three sessions is a lot. When I ran that for my brother and stepsisters, they got through it in a couple hours.

Thank you for all your suggestions. I think we’ll be fine now 

Quote from HomebrewMindFlayer >>

I have the same problem! I usually get through one encounter a session, sometimes 2. my encounters (not just combat) take my players waaaay tool long! and I have no idea why. we don't have rule discussions, tactics discussions, anything like that very often, slowing the game.

 Exactly. My group doesn’t know why we are so slow either

Number 1: no rules arguing, there's almost always at least one person at the table who is rules guru, or the DM can just rule something until further notice.

Number 2: Don't roll new initiative every round, this just slows everything down.

Number 3: Use initiative cards ( usually a index card with a number written on it ).  

You can group initiative all of the monsters - meaning they roll once and all go at the same time.

You can use the average roll for damage on the monster detail page instead of rolling damage.

You can ask yourself if you're having fun. If you are, don't worry about it. The number of rooms cleared isn't always a good indication of success.

Quote from SpeedyTabaxi_CatsForLife >>

I'm playing in a campaign, mostly RP, but when it comes to combat, we are horribly slow. For example, our first dungeon took three sessions. THREE SESSIONS! That's just way too much. So, anyone have some suggestions to speeding up combat?

 How many combats were in that dungeon? How long are your sessions? What other stuff was going on? Depending on its scale, taking three sessions to complete a dungeon may not be out of line.