Question about CR Equivalencies?

[Snakebearer]

I've had some problems with building encounters for a while now. So I checked around on these forums for examples, and I think I got the idea nailed down now.

I have 4 PCs at lvl 5, which makes their APL 5.
Which in turn makes them viable for facing a challenging encounter with a CR of 6.
To make CR 6 encounter, I have to check the exp total (2400) for such an encounter and build from that. Correct?

Let's say I want my characters to face a group of goblins.
Example: 1 Goblin Druid 4 (CR3, 800 exp), 1 Goblin Ranger 3 (CR 2, 600 exp) and 5 Goblin Chitterbacks (CR 1/2, 200 exp).
This is a good CR 6 encounter, right?

Now, for the Table: CR Equivalencies.. How the heck is that intended to work? It's not mentioned in any rule text, and it seems any forum posts about it blatantly ignore it?
What's the purpose of the table? I mean, according to what I've read, CR does not stack in any way like this? Since I'm only looking at the EXP Budget when building the encounter?

I mean, does this mean I'm off? I have 7 creatures fighting, and they are of mixed CRs individually. How do I apply the CR Equivalencies here? Or is it just there for looks?
Do I take the encounter CR and add CR to it because of their numbers? That sounds ridiculous, but looks like the implied use at first. Or is it to bunch up several of the same creatures to one CR (Which in effect says nothing since I already have the numbers and exp pre-determined?)

Or, do I have to build my encounters in a completely different way to have any use for that table?
I'm playing with the idea of building monsters of my own. I made a Graveknight Goblin Fighter 5 for lols. It has a CR of 6. (4 as base + 2 for template). Meeting him alone gives the party 2400 exp. Do I use this table if I want them to meet him and his identical twin brother? Which nets them 4800 exp total, which is identical to the CR+2 = CR8 = 4800 exp.
This would imply that the real use for the table is if I reverse engineer my encounters. Making the monster first, before deciding on any budget?

Please help me clarify this. XD

/ Snake

[Xan_Ning]

Snakebearer wrote:

I made a Graveknight Goblin Fighter 5 for lols. It has a CR of 6. (4 as base + 2 for template). Meeting him alone gives the party 2400 exp. Do I use this table if I want them to meet him and his identical twin brother? Which nets them 4800 exp total, which is identical to the CR+2 = CR8 = 4800 exp.

Essentially this. It's just a fast way to determine the CR of an encounter with multiple identical monsters.

[PhelanArcetus]

Basically there are two ways to address your encounter construction when you have multiple of the same monster.

You can either add them all up directly, as you described above, or you can treat the Goblin Chitterbacks as one creature via the CR equivalencies. In the end, it's going to add up the same (adding +4 to CR 1/2 is awkward, in this case). Basically, the CR Equivalencies table simply allows you to reference an XP total directly on the table for a group of identical monsters.

If you study a few points on the table, you'll see that, in general, if you take CR X's XP value, and multiply it by Y creatures, you'll get the same XP total as CR X+Z (where Z is the modifier from CR Equivalencies).
Examples starting at CR 1:
X = 1; CR 1 is 400 XP
If Y=2, then Z=2; 400 x 2 = 800 XP; CR 1+2=3 is 800 XP.
If Y=3, then Z=3; 400 x 3 = 1,200 XP; CR 1+3=4 is 1,200 XP
If Y=4, then Z=4; 400 x 4 = 1,600 XP; CR 1+4=5 is 1,600 XP
If Y=6, then Z=5; 400 x 6 = 2,400 XP; CR 1+5=6 is 2,400 XP
If Y=8, then Z=6; 400 x 8 = 3,200 XP; CR 1+6=7 is 3,200 XP
If Y=12, then Z=7; 400 x 12 = 4,800 XP; CR 1+7=8 is 4,800 XP
If Y=16, then Z=8; 400 x 16 is 6,400 XP; CR 1+8=9 is 6,400 XP.

So in your case, you could view it as:
1 Goblin Druid 4; CR 3 = 800 XP
1 Goblin Ranger 3; CR 2 = 600 XP
5 Goblin Chitterbacks; CR 1/2 = 200 XP x 5 = 1,000 XP
Total = 2,400 XP

Or as
1 Goblin Druid 4; CR 3 = 800 XP
1 Goblin Ranger 3; CR 2 = 600 XP
1 Goblin Chitterback; CR 1/2 = 200 XP
4 Goblin Chtterbacks; CR 1/2 each, 4 creatures yields 4 1/2, which seems to round down to 4 in this case; 800 XP
Total 2,400 XP

Honestly if you can do multiplication, there's little use for the table, which I believe is largely there as a holdover from the 3.5-era CR method, which did not translate so simply to XP.

The table can be useful if, say, you want the party to face a bunch of enemies. You can quickly reverse engineer a CR for the individuals from your final CR with this table (you can also do it with division, though).