Challenge Ratings

Some related questions--

I'm slightly confused as to how to calculate a party's level for the purposes of generating challenge ratings. The DMG says to average the levels of the party members... but that really doesn't make sense to me. If you were to average the party level of three 6th level characters or the party level of eighteen 6th level characters, you would come up with the exact same EPL... and that doesn't seem right. More players should add up, shouldn't they?

It seemed to make more sense to myself and my players that adding up the ECL of the party engaged in battle and the CR of the monsters being fought should equal for a fair fight. And by this philosophy, my players have been surviving challenges, but sometimes only JUST BARELY and by the skin of their teeth.... so something feels amiss.


My next question relates to the subject of dragons. I've read a number of times on the boards here that the CR of dragons is HIGHLY underestimated. What would you think is an ACCURATE CR for dragons? To tie into the question above, what party level would you consider capable of handling a great wyrm? (How many members in that party as well) If there's a thread already on this subject, a link would be nice (I'd search but I can't)


For background, I'm asking this because I'm trying to come up with a race (only loosely based on the phoenix) that is a racial enemy of dragons, and I need to gauge where to stick them in terms of power level at varius levels, and also determine a CR for them...

The whole CR system is based on an assumption that the party size is 4. Period. CR ratings indicate the average level of a 4-member party who can reasonably confront it.

If you have a smaller or larger party, you might wish to guage EL's, using the standard double-numbers-adds-2-EL rule. If you're running a party of 18 PC's, the simplest thing to do is just throw in x4.5 as many monsters as you'd otherwise use (18/4).

In my opinion, dragon CR's could go up by +2 and be consistent with the rest of the rules (working from 3.0 here).

Probably others will expand upon these principles.

I'm not sure exactly what you describe by "adding the party's ECL", but if you determine what CR the party could be if it was the threat, you'rea headed for TPK city.

A character of 9th level is a CR9 encounter. A group of four 9th level characters is a CR13 encounter. This means that a group of four 9th level character would have lots of difficulty defeating an equivalent group, which makes sense. If two identical groups face off, there's basically a 50/50 chance that either group will win. Whatever the result, it's highly probable that the winning camp will suffer losses.

The double-the-creatures-add-2 rule dcollins speaks of can indeed be expanded to take care of parties that do not consist of 4 characters.

A party of 1 character of level X should face creatures/encounters of CRX-4
A party of 2 characters of level X should face creatures/encounters of CRX-2
A party of 3 characters of level X should face creatures/encounters of CRX-1
A party of 4 characters of level X should face creatures/encounters of CRX
A party of 6 characters of level X should face creatures/encounters of CRX+1
A party of 8 characters of level X should face creatures/encounters of CRX+2
A party of 12 characters of level X should face creatures/encounters of CRX+3
A party of 16 characters of level X should face creatures/encounters of CRX+4
A party of 32 characters of level X should NEVER BE FORMED.

AR

Altamont Ravenard said:

The double-the-creatures-add-2 rule dcollins speaks of can indeed be expanded to take care of parties that do not consist of 4 characters.

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This is basically true, but in practice it's not quite accurate. A party of 8 4th-level characters will not be quite as tough as a party of 4 6th-level characters.

For instance, the lower-level party will have fewer hit points per member. If a battle leaves a Ftr6 wounded but alive, he can be healed and the adventure can continue. The same battle would probably kill a Ftr4, and losing a member (or expending treasure to have him raised) only makes the group weaker.

Fieari said:

It seemed to make more sense to myself and my players that adding up the ECL of the party engaged in battle and the CR of the monsters being fought should equal for a fair fight. And by this philosophy, my players have been surviving challenges, but sometimes only JUST BARELY and by the skin of their teeth.... so something feels amiss.

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Sounds like you're making an error common to DMs new to the CR/EL rules. Adding up the EL (not ECL, which is Equivalent Character Level) of the party and throwing it against monsters with the same EL means your party is exactly as strong as the enemy and has a 50% chance to win. Which is why they're surviving by the skin of their teeth.

A "balanced encounter" in D&D is not one equally as strong as the PCs. It is one which can pose a challenge but which the PCs should always (barring very unusual circumstances) win. For example, a 5th lvl NPC Wizard is a "balanced encounter" for a four member party of 5th lvl characters.

It is assumed in the rules that such balanced encounters make up the bulk of a party's combats. Vary it with some that are tougher and some that are easier, and you're good to go.

Try this:

http://arcady0.topcities.com/Encounter_Calculator.html

Another method I've seen was posted in this over at the Wizard's boards some time back:

Nadaka said:

My stanard response to this oft asked question. On the old boards, this question was asked so often, I could spend hours every day to type out an individual response to all of them. So, I decided to create a standardized response.

To answer your question refer to the red highlighted section, and then the green highlighted section.

CR, EL, APL, and what in the infinate planes of the abyss does this all mean.

CR = Challenge rating
A number that represents the relative difficulty to overcome a challenge, most often a creature or trap. It is also used when determining the experience point award for overcoming a single challenge, by combat, sneakyness, diplomacy, or any other method. If you face multiple challenges in the same encounter, use each individual CR to determine XP and award that sum to the player characters in equal shares. (With any cohorts recieving a half share.)

EL = Encounter Level
A number that represents the relative challenge of one or more challenges encountered at the same time. It is used as a guide to show the relative difficulty that your party will have against multiple challenges. It is *NOT* used to determine XP.

Determining EL
when one challenge is encountered: EL = CR. Example, one ogre (CR 2) is EL 2.

Multiple creatures:
When dealing with CRs of 2 or below: Add CRs together. Example, 2 orcs (CR 1/2) are EL 1. 2 1rst level paladins (CR 1) are EL 2 and 3 kobolds (CR 1/6) are EL 1/2.
When dealing with CRs of 2 or more: doubleing the number of challenges increases the EL by +2. Example, 2 ogres (CR 2) are EL 4, 4 ogres are EL 6, 8 ogres are EL 8.

What does EL mean?
EL is not a linear progression, it is exponential.
An EL two points higher than another is twice as difficult, an EL 4 points higher is 4 times more difficult, an EL 6 points higher is 8 times more difficult, an EL 8 points higher is 16 times more difficult, etc.

APL = Average Party Level
Technically the average level of a party of 4 PC classed characters. You can find APL for parties of other sizes by finding thier EL and subtracting 4.

EL = APL is a standard challenge. A standard challenge is meant to use about 20% of a parties resources. (HP, Spells, ammunition, charged magic items, etc.) It will generally always result in the challenge being overcome. A normal party can safely take 4 to 5 such challenges before needing to replenish thier resources. There is a very small chance that a PC could be killed. This would only happen if A) the player did something stupid, B) there was some really bad luck, or C) the challenge focused 100% of its offence against a single PC. And even then it is quite unlikely.

EL = APL +2 is a diffucult challenge. A difficult challenge is meant to use about 40-50% of a parties resources. (HP, Spells, ammunition, charged magic items, etc.) It will usually result in the challenge being overcome, but there is a very small chance that it will not be. A normal party can take about 2 such encounters before needing to replenish thier resources. There is a small but very real chance that one or more PCs could be killed. As above but the circumstances need be less extreame.

EL = APL +4 is a very diffucult challenge. A very difficult challenge is meant to use 80% to 100% of a parties resources. (HP, Spells, ammunition, charged magic items, etc.) There is only a 50/50 chance of overcoming this challenge. Taking more than one such challenge before replenishing a parties resources is tantamount to suicide. It is very likely that one or more PCs will be killed, and a good chance that all will be if they fight to the end.

EL = APL +5 to +7 is an extreamely difficult challenge. An extreamely difficult challenge is meant to use 100% or more of a parties resources. (HP, Spells, ammunition, charged magic items, etc.) There is less than a 50/50 chance of overcoming the challenge, But there is a very small chance that the PCs can succede. A normal party can not take even one such encounter before needing to replenish thier resources. One or more PCs PCs face an almost certain death if they do not flee the encounter.

EL = APL +8 or more is an overwealming challenge. The odds of defeating an overwealming challenge are minute at best. The resources it would consume are irrelevant. The average party can not hope to take one encounter of this level before needing to rest. All PCs will almost assuredly die without some kind of miracle or DM intervention if they do not flee from this battle.

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That is the standard explanation that I have used. I have encountered a potentially better explanation made by Martymer board member #25519.

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The system in the Encounter Calculator is:

To find Effective Level do:
(2^(PC level)

for each PC, then add it up.

We'll call the total of that PartyPower.

Party Effective Level = 2 * ((Log base-2 of E) * log of PartyPower)

As long as you have 4 PCs this 'Effective Level' will equal the Party's average level.

Log base-2 of E is a mathematical constant roughly equal to 1.4426950408889634

AuraSeer said:

This is basically true, but in practice it's not quite accurate. A party of 8 4th-level characters will not be quite as tough as a party of 4 6th-level characters.

For instance, the lower-level party will have fewer hit points per member. If a battle leaves a Ftr6 wounded but alive, he can be healed and the adventure can continue. The same battle would probably kill a Ftr4, and losing a member (or expending treasure to have him raised) only makes the group weaker.

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True…

…but the lower level party will have a lot more actions per round. That’s a lot more opportunities for crits, a lot more people to use that wand of fireball (or they can have a lot of wands for more than one FB per round), etc.

large parties of lower level can bring all their force to bear at once. But as you said, they don’t have the staying power.

IMC I recently sent a bunch of little guys after the party. In the first round they ALL threw spears at one PC and did piles of damage. But then they had nothing left, and the party mopped them up in a few rounds.

-Tatsu