Calculating CR

[ramrod]

Hi guys,


I just wanted to check my understanding of CR before I went ahead and populated my campaign with mobs that are not appropriate!

If I have a fairly average party of four or five pcs, all at level 5. If I throw them a CR rating 5 encounter, say 5 1 CR monsters, or 1 5 CR monster, or two 2 CRs and one 1 Cr monster... Those would be moreorless appropriate for them and they should be able to handle four or five of those encounters before they need to rest?

Obviously, there would be differences in that, one 5 cr monster should potentially be easier to deal with due to action economy... But is this roughly correct?

As a bonus question - if this is correct, roughly how many encounters should I do between levelling up, I know I can do it arbitrarily, but i want to see if my dungeon will be populated enough to be equivalent to about three levels!

Thanks in advance!

[Malimar]

The CR system is widely held to be broken and lots of people will tell you that you shouldn't put much faith in it. That said, it's what there is, so until you have a good intuitive sense of what the party can handle, go ahead and use the CR system, it's a decent enough guideline.


You want to read chapter 3 of the Dungeon Master's Guide, if you can get access to it. It explains all this stuff.


CR for multiple monsters isn't additive. The rule is: every time you double the number of monsters, you add 2 to the Encounter Level. So, for a level 5 party, you want four CR1s, three CR2s, two CR3s, or one CR5. Or a pair of CR4s and a CR2, or 8 CR1/2s (CRs below 1 use a different rule), or anything else in that general range -- you can mix it up a bit, nobody will notice.


The game assumes a party can take four equal-CR encounters in one day. The XP system is set up so that it takes roughly thirteen equal-CR encounters for a party of four characters to level up. If you want to use XP, you should probably use a calculator (http://www.d20srd.org/extras/d20encountercalculator/) to figure out the totals, rather than doing the math by hand. If you don't want to use XP, there's no need to stick to the 13-encounters-per-level thing -- a lot of people just level the party up whenever they come to a natural "you just accomplished something big" point, be it finishing a dungeon or defeating a boss or what-have-you, without regard to actual encounters handled.

[KillianHawkeye]

Erm....... not quite. CR is used for calculating experience, but to determine the actual expected difficulty you need to calculate the Encounter Level. This is not done by simply adding the CRs together. Typically, doubling the number of creatures increases the EL by 2, but there is a chart for specific numbers of different CRs.

I suggest reading "Challenge Ratings and Encounter Levels" starting on page 48 of the DMG.

[Urpriest]

Hi guys,


I just wanted to check my understanding of CR before I went ahead and populated my campaign with mobs that are not appropriate!

If I have a fairly average party of four or five pcs, all at level 5. If I throw them a CR rating 5 encounter, say 5 1 CR monsters, or 1 5 CR monster, or two 2 CRs and one 1 Cr monster... Those would be moreorless appropriate for them and they should be able to handle four or five of those encounters before they need to rest?

Obviously, there would be differences in that, one 5 cr monster should potentially be easier to deal with due to action economy... But is this roughly correct?

As a bonus question - if this is correct, roughly how many encounters should I do between levelling up, I know I can do it arbitrarily, but i want to see if my dungeon will be populated enough to be equivalent to about three levels!

Thanks in advance!

You're confusing CR and EL.

CR only applies to individual monsters. EL, or Encounter Level, is a measure of the challenge of an encounter.

One CR 5 monster, encountered alone, is EL 5, which means it is indeed an appropriate challenge for a 5th level party of four.

Your other examples make it look like you think CR is additive. CR is not additive! Two CR 3 monsters is not an EL 6 encounter, for example.

There is a table that sets out what combinations of CRs give you what ELs on page 49 of the DMG. The rule in general is that two CR X monsters are an EL X+2 encounter, while a CR X monster and a CR X-1 monster are an EL X+1 encounter. You can apply those two rules to EL as well, which allows you to construct encounters with any number of creatures.

Of your examples, five CR 1 creatures can be EL 4, 5, or 6 (EL is a bit fluid at the lower levels), two CR 2 monsters and one CR 1 monster is roughly EL 4, maybe EL 5.

XP is based on CR, rather than on EL, EL is just a guide for when players can fight the monsters in question. The players will be able to handle about four encounters of their EL before needing to rest, and will usually gain a level after 13 encounters of their EL.

[ramrod]

Thanks, I'll read the dmg again on those pages. It is still confusing the hell out of me lol, I thought that, looking at the examples that I had looked up that it seemed a bit weak!

[Telonius]

Thanks, I'll read the dmg again on those pages. It is still confusing the hell out of me lol, I thought that, looking at the examples that I had looked up that it seemed a bit weak!

I'd also suggest the Encounter Calculator here (http://www.d20srd.org/extras/d20encountercalculator/). [EDIT: looks like Malimar already posted it.] Just plug in the numbers for the CR of each enemy, and the effective character level of the party, and it will tell you how much experience each character should get for defeating the encounter. I've found it saves a lot of time and math headaches.

[Chronos]

Also note that not all encounters should be exactly at the party's EL. They should occasionally meet easier encounters, and also occasionally meet harder ones (especially bosses, or things that they can run from without losing their main objective).