D&D 5E Challenge Rating formula...

[Tormyr]

The original encounter design guidelines are flawed and overstate encounter difficulty when you have monsters at very different CRs (and the "XP multipler" is a clunky concept that makes designing encounters difficult). I haven't looked at the update to the DM Basic Guide from November in detail, but it looks much the same (I presume the DMG is similar).

I recommend Gobelure's thread on how to modify the encounter design guidelines to fix this problem, so that you don't need an "encounter XP multiplier." http://www.enworld.org/forum/showthread.php?367697-Encounter-difficulty-how-to-fix-it The key is that in Gobelure's new tables PC and monster power scales more slowly with CR/levels, so that you don't need the "fudge factor" of the "encounter XP multiplier."

Here's how I described the issue in that thread:

The DMG and basic update said to ignore creatures that are too small of a contribution compared to higher CR creatures in the same encounter. In essence, the DMG says to ignore the kobolds next to the dragon. PEL virtually ignores them as it is.

My encounter building spreadsheet posted further up also reports the result IN PEL. It also smooths out the XP multiplier so there is not that jarring bump when adding a certain number of PCs or monsters.

 

[I'm A Banana]

The original encounter design guidelines are flawed and overstate encounter difficulty when you have monsters at very different CRs (and the "XP multipler" is a clunky concept that makes designing encounters difficult).

I think this is a good example of something that I find rather inexplicable: people have strong frickin' opinions on what constitutes a good CR system.

I find the 5e RAW works well for my general "how many licks does it take to get to the toostie roll center of a tootsie pop" purposes. Suggestions that it is somehow objectively inadequate are ill-founed, IMXP, though of course it may not always perform exactly as any one individual may expect.

 

[Jester David]

Just throw whatever seems right and award experience based on how difficult the party found the fight: easy, difficulty, or deadly.

 

[fjw70]

How about "it doesn't even vaguely match the 5e guidelines" as an objection? I mean, just work it out in some samples - that system doesn't even come vaguely close. in fact it almost seems like it comes up with D&D Next playtest type results rather than 5e-based results.

I haven't checked all his numbers but the philosophy is sounds.

1) Determine the XP needed for a hard encounter with 2 monsters per PC, 1 monster per PC, and 2 PCs per monster.

2) Use easier/less monsters for less than hard encounters and tougher/more monsters for harder than hard encounters.

 

[PnPgamer]

Formula for challenge rating? I need to get my helmet and crew and tune up my ride!

 

[cthulhu42]

Just throw whatever seems right and award experience based on how difficult the party found the fight: easy, difficulty, or deadly.

That's generally what I do. I've been DMing long enough that I can usually scan a stat block and know what my PC's can handle.

However, this being a new edition for us, I've been trying to get a handle on some of the minutia rules, as well as trying to see just how well a CR"x" creature stands up to my group of 4 PC's. It seemed like a good test of the system, not to mention pretty eye opening. But rather than have them fight just a single creature of their CR, I thought it'd be good to throw multiples at them, but therein lay the problem of determining how many of what kind of creatures added up to the target CR.

One thing I'm finding interesting is that the monsters scale pretty quickly, and generally speaking, even a single creature of a given CR is proving it can hold it's own against the PC's. I've been running them on a sort of power leveling game in order to familiarize ourselves with the rules, so I've run them from 1st to 7th pretty quickly, with 2 to 3 encounters between levels. The idea being to get them to 20th, then start from scratch and begin an actual campaign.

Anyway, I've been mixing it up a bit, but in general I've been tryign to get as close to the party's CR as I can, and I've been surprised to the monsters kicking some PC butt. I'd say in at least 75% of the fights at least one PC goes down, and sometimes two of them hit the floor.

I don't really know how that compares with earlier editions because I usually ignore CR's, but I seem to remember that the few times I did throw a CR appropriate monster at my 3.5 group, they mowed it down pretty quickly.

Not so, this time around.

In fact, every time they level my group crows like crazy about all the cool new kick butt abilities conferred on them by the level gain, and I always think, "Wow, they're going to start crushing these beasts!" But then a Bullete pops up out of the ground and drops the cleric with his first bite, or a cyclops knocks the warlock into next week with a tree trunk.

Honestly, I've always thought the CR system was flawed anyway. Terrain and strategy make such a huge difference. I threw a pair of chuul at my group (one max hp, the other average), which was actually more than double the party's CR level, but it was on flat ground. It was a tough fight, but I wasn't too worried, and they eventually beat the chuul down.

The very next encounter (after a long rest) was with a single barbed devil who attacked them from a 30' high balcony. He put the warlock down not once, but twice, then knocked the fighter out, and had the sorcerer at single digit hit points before the cleric managed to finish him off.

Anyway, that's a long way of saying, I was just curious if the math was out there. I'll probably just wing it like I always do. It's worked for 20+ years, after all.

 

[TerraDave]

I think this is a good example of something that I find rather inexplicable: people have strong frickin' opinions on what constitutes a good CR system.

I find the 5e RAW works well for my general "how many licks does it take to get to the toostie roll center of a tootsie pop" purposes. Suggestions that it is somehow objectively inadequate are ill-founed, IMXP, though of course it may not always perform exactly as any one individual may expect.

I have also found that it works pretty well. Better for me then, well, the last few editions. If you want to hedge a little, add some numbers, maybe as a second wave, but stay at or below CR. But this is not really needed.

In any case, I don't really think 5E is about fine-tuning encounters. In part because that's something of a fools errand. In part because 5E's fast and furious combat is always going to have some swing to it. In part because the flat math on the one hand, and the depth of players resources on the other (at least past the first few levels) means that you shouldn't have to worry about it as much.

 

[TerraDave]

...
Anyway, I've been mixing it up a bit, but in general I've been tryign to get as close to the party's CR as I can, and I've been surprised to the monsters kicking some PC butt. I'd say in at least 75% of the fights at least one PC goes down, and sometimes two of them hit the floor.

...

Also my experience. I am glad to see it holds at higher levels!

For me, that's the sign of a challenge, but its very different then a TPK. Haven't really come close to one of those yet.

 

[Sunseeker]

Just throw whatever seems right and award experience based on how difficult the party found the fight: easy, difficulty, or deadly.

What I don't like about this is that it doesn't properly reward creative solutions that make what are designed to be hard fights much easier. It encourages players not to play at their best because that makes the fight "harder" and any player who isn't completely oblivious to the fact that the DM is making up how much XP they get will figure out that those numbers go up when they have a "harder" time.

If the fight is absolutely trivialized by the party, the best thing the DM can do is come prepared next time for a more proper challenge. Otherwise I would reward my players more for creative thinking that made a fight easier than for not doing so and making the fight harder than it needed to be.

 

[Jester David]

What I don't like about this is that it doesn't properly reward creative solutions that make what are designed to be hard fights much easier. It encourages players not to play at their best because that makes the fight "harder" and any player who isn't completely oblivious to the fact that the DM is making up how much XP they get will figure out that those numbers go up when they have a "harder" time.

If the fight is absolutely trivialized by the party, the best thing the DM can do is come prepared next time for a more proper challenge. Otherwise I would reward my players more for creative thinking that made a fight easier than for not doing so and making the fight harder than it needed to be.

If you're throwing away the book and rewarding based on challenge, then it's easy to adjust. If it should have been deadly by creative use of spells or the terrain made it a cake walk, better xp.

The catch with trivializing encounters is that it quickly leads to rapid level gain by the book. Optimized and coordinated groups with the right synergy can take apart monsters (in any edition) and just adding more monsters will rocket them up levels.