Part of the equation is what happens outside of combat.  Declaring actions and resolving combat is relatively time-intensive.  If each player averages 1 minute for their entire action sequence, that's pretty good.  Four players plus the DM might mean 5 minutes per round, and 3-4 rounds of combat might end up being 15-20 minutes.  Breaking every action up into 1-second increments (and thus multiplying how many times you have to go around to everyone) increases the time it takes dramatically while creating more 'non-action spaces'.  Giving the player enough actions to do things but not so much that combat completely changes is a balancing act.  The number of actions MATTER. 

Now, whether you say that number of actions is 6 seconds or 15 seconds of real time has more to do with what you're comfortable with.  If a combat is 3-4 rounds, that's 18-24 seconds of 'game time'.  Personally, I'd feel a little more comfortable with that being a minute or more - so people who hear combat have a chance to do something to prepare if nothing else.  I think 10/12/15 are all good numbers and better than 5 second/6 second rounds in terms of balancing a reasonable 'set' of actions and having the appropriate amount of time happen in the world while combat is happening. 

About 10-12 seconds seems best. I did like my friend Bob's system with a 15 second combat round broken down into 4 phases. It was designed to integrate squad level & individual combat; the squad leader making decisions each round while combat resolved in phases. It suited the different durations of the OODA loop at the two scales - not that we had heard of John Boyd in 1991.

I don't care about the specific in-game duration of a round because I want characters to be able to do dramatic stuff in combat, play off of enemies and allies, taunt, make speeches, etc. What's more relevant to me is making sure the combat isn't just Rock-em-Sock-em robots and that combats can progress characterization and plot.

Another element that can play a factor in figuring out an ideal "time per round" is range and movement.

Basically, if your system uses any sort of miniatures, even optionally, then you need turns long enough that pieces can move at least one unit of distance, but not so long that they can cross a reasonable play area in a single round.

So for human scale and movement you're looking at about 15-ish ft/s at a run... so 6 seconds is a run/charge of 90'... eighteen 5' squares (or 1.5 feet at an inch per square) or nine 10' squares (9" at an inch per square). At a minute that's a run of 900' during the round or ninety 10' squares or 7.5 feet at an inch per square (15' using 5' to the inch).

That's one reason WotC's rules for modern vehicles have always had issues; because they kept using 5' squares.

Meanwhile games custom built to take that speed into consideration like Mekton use both large units per inch (Mekton uses 50m hexes) with short real time turns (10 seconds) to reflect the great speed that most mecha can achieve.

So turn length isn't just an independent variable, but one that interplays quite heavily with movement and range.

I like 10 seconds.  However I really think it depends on what is happening.  If two groups are charging at each other from a long ways away I don't really want to go through 20 rounds of "I keep going" to reach the other group.  Similarly playing hide and seek in limited visibility.  On the other hand if I wanted to do a good job simulating the various martial arts I'm familiar with, 1 s rounds are about right.  I've yet to find a system that does a good job with variable length rounds though.

3.6 second rounds because speeds in meters per turn are equal to speeds in kilometers per hour.

Quote from: Steven Mitchell on August 10, 2021, 08:26:11 AM
What is your optimal duration for combat rounds and why? 

It makes the old D&D 1 minute round not look so strange.

1: In game it honestly does not matter how long the round really is as long as you know the progressions of initiatives, cooldowns, chargeups, etc.

Out of game I usually let a combat take as long as needed with occasional prods to get moving on those rare occasions someone is stuck deciding. And for me that has been very rare. Usually my players have their actions planned out by the time its their turn. I rather like the overall speed that 5e combats tend to play out in. On average they tend to last about 5 minutes. Sometimes longer, sometimes shorter.

2: AD&D really had a good system going with its rounds and segments of rounds to be used as needed.

In the fantasy games I am most familiar with, the rules say either 1 minute or 5 or 6 seconds. Yet what players are allowed to do in a round tends to be roughly the same in all those games. When I think about what makes sense, I arrive at ten seconds, and that is how I visualize things regardless of what the rules say. I can't remember the last time that number made any difference. Probably never.

Quote from: Wntrlnd on August 10, 2021, 09:10:59 AM
I recall reading a post (either here on on Reddit) about GURPS having 1 second rounds and how they are way to short and one poster pointed out how 10-12 seconds are more realistic in a squad combat scenario on how first Observe, Plan an action, Order the squad have them Perform the action. -But I think that would be a game focusing on group combat not individual combat.

I never read that post so I don't know to which game it refers to. However there is a jet warfare boardgame, "Air Superiority" designed by a real jet fighter pilot, J.D. Webster. In the designer's notes Webster says that he choose "12 seconds/turn" because, in his experience, that's the length of the aforementioned decision cycle by a pilot in a jet vs. jet combat.

3E GURPS' 1 seconds turns were the worst rule in the game. It was easy to see how "acting" was the result of the decisions and observations made in a sort of "external time" - i.e. while other players and the enemies were taking their turns.

Even worse, if for some reason you character blew his nose you were out of the game for 5-6 rounds or more, so, possibly, one hour of real time. I had players who hated casting a 3 seconds casting time spell because it meant pulling out a book and wait (no phones to fiddle with at the time).

We ended up house-ruling that a round was 1d6 seconds long. After each round the GM rolled a die and moved the time forward accordingly. The reasons for a "6" were narrated: someone checking the result of his firing, two fighters circling each other with their swords, sudden lulls in combat and so on.

It was not perfect, but it added a lot of tension, combat flow was more realistic, and it killed the "I don't bother about the spellcaster: he will cast his spell during the next session anyway!" problem.

Right now, I like CoC 7E rounds duration: "Enough for everyone on the scene to do something meaningful".

One thing I have noticed may be a factor is that the ratio to round time versus the next unit up affects decision making for the players.  A good example is D&D when there are a lot of 1 minute spells.  With a round of six seconds, the spells are nearly always "all combat long".  In 5E, I think this is deliberate, so that they can use "1 minute" as the duration without saying "1 fight" and invoking the angst of people who didn't like encounter duration in 4E.  On the plus side, you effectively don't need to track the duration of such spells.

When I switched my play test from 6 second rounds to 10 second rounds, it changed the feel of that.  Now, I know that most fights are over in 6 rounds, because I designed the system to move fairly quick.  However, the players are used to 5E.  So for them, they hear "1 minute" and they start thinking that the spell will wear off during a fight. And it could if they monkey around, but more likely only if both sides whiff a lot early.  The end result is that they don't monkey around, because they know the counter is ticking.  I need to keep track of it (which is trivial), they hurry things up, which means I don't really need to track it for most fights.

Will be interesting to see if this holds up over time as players in the test discard their D&D influence and absorb how the game works.

5-10 second rounds for Cryptworld, but I think a bigger issue is how long combat should take in real time. I just had one battle last week between my party and 5 zombies take 1 1/2 hours to finish, and the creatures almost wasted them. In game time the battle amounted to around 1 minute. As grueling as it was, I think it makes sense for a lot to happen in a 1 minute battle, and that no creature is necessarily an "easy" 20 second kill.

Quote from: Chris24601 on August 10, 2021, 10:50:06 AM
(personally for mecha/modern combat I default to 3 second rounds with characters able to do two things during their turn; i.e. move+shoot, move twice, shoot twice, aim+shoot, etc.).

This is my favorite as well, which I use in my homebrew designs. Something like 3.X, where each round, you can do one of the following:

* move and attack
* attack and move
* move twice
* use a skill or a power

Spycraft modified the 3.X action economy so you could attack twice. But I don't like the later versions of 3.X where they added swift rounds (like Star Wars Saga) which is too fiddly.

The actual seconds of a round (3, 5, 6, 10) doesn't matter that much to me.

Quote from: Reckall on August 12, 2021, 06:47:58 AM
3E GURPS' 1 seconds turns were the worst rule in the game. It was easy to see how "acting" was the result of the decisions and observations made in a sort of "external time" - i.e. while other players and the enemies were taking their turns.

Isn't that true of any RPG, though? I don't mind it if a player makes a decision from information observed when it's not his turn, assuming his character would have seen it, of course.

Quote from: Reckall on August 12, 2021, 06:47:58 AM.
We ended up house-ruling that a round was 1d6 seconds long. After each round the GM rolled a die and moved the time forward accordingly. The reasons for a "6" were narrated: someone checking the result of his firing, two fighters circling each other with their swords, sudden lulls in combat and so on.

In the 3E Combat Compendium there was an optional rule for lulls in combat, which sounds something like what you describe.

I'd say anything much beyond 3 or 4 rounds of combat, starts to drag.

Of course, an epic battle with a big bad could certainly go 5 or 6 rounds.

I'm in favor of short turns, and fast gameplay.

Quote from: Jam The MF on August 12, 2021, 11:05:13 PM
I'd say anything much beyond 3 or 4 rounds of combat, starts to drag.

All depends upon the context. With side-based rounds and a streamlined system, each round could be fast enough that having a few more might feel fine. Especially if the game is a modern/sci-fi game with a ranged combat focus. IMO - melee combat focused systems need to have fewer rounds generally as standing and swinging at each-other can usually only be tense for a round or three at most. There's more leeway if you're running from cover to cover and tossing grenades in a firefight etc.

But I totally agree with you for D&D style systems.


As to the length of each round - for fantasy games, I'd say 6-12 seconds, while for games with firearms I like shorter rounds for two reasons.

1. With a  gun every 3-4 seconds is enough to make significant choice of target.

2. More importantly - the shorter rounds let you lower movement speeds substantially. If characters have 10 seconds to move before being shot at, it's far too easy to close the distance to melee - or you have to add extra rules etc. to give an edge to firearms. With 3 seconds you can even say that moving more than a few feet in the round costs you your attack without it feeling wonky.