Equivalent player class level compared to Creature CR

[Dansun]

Is a Challenge Rating 3 creature roughly equivalent to a level 3 player class?

Say I want to play as a Doppelganger (CR 3) alternative race and progress him as a bard. Would it be fair to say he is equivalent to a level 4 base class as a 1st level bard?

How would you account for a Doppelganger (CR 3) abilities in regards to advancing him as a player character?

http://paizo.com/pathfinderRPG/prd/monsters/doppelganger.html#_doppelganger

[Mort the Cleverly Named]

It is hard to call them even "roughly equivalent," but the Monsters as PCs guidelines do say to treat a monster as a character of its CR. So, a Doppleganger Bard 1 would indeed be considered equal to a 4th level character. It would also gain an extra level between levels 5 and 6.

[Starglim]

A CR 3 creature is roughly equivalent to 20% of four 3rd level characters when using its best abilities in a brief fight, so probably a fair bit less than equivalent as a PC. Class levels that synergise well with its abilities might make up for it.

[blackbloodtroll]

If you nab the Advanced race guide playtest, you can figure out the power level of the goal creature.
The book itself will be out very soon.

[Ironballs]

The CR of a creature that's based on PC's class levels is level-1,
so a goblin ranger 5, will be CR 4.

if it uses NPC levels, then the CR is level-2, so a goblin warrior 5, will be CR 3.

[Remco Sommeling]

Ironballs wrote:

The CR of a creature that's based on PC's class levels is level-1,

so a goblin ranger 5, will be CR 4.

if it uses NPC levels, then the CR is level-2, so a goblin warrior 5, will be CR 3.

That only works for NPC's, if you give them PC treasure paizo goves them +1 CR usually

In my opinion that should mean that a doppelganger fighter level 1 NPC would be CR 4, giving them wealth equal to a 5th level PC should enhance the CR by +1, roughly CR 5, about equal to a PC fighter lvl 5.

A bard is probably not a favored class so a PC equivalent bard level 2 would be CR 5.

The rules are a bit muddy, I usually just assign CR according to what I think is right by the numbers and abilities, adjusting official CR up or down a bit, keeps it possible for me to create some inefficient NPC's that are still rather interesting as villains.

[Knight Magenta]

The whole CR = Level is a weak assumption. You have to look at the creature's abilities in relation to what an equal level character could do. For example, the at-will detect thoughts and shape change can be overpowering in a city-based more social campaign, but will be almost worthless in a dungeon crawl.

Also, the doppelganger has four racial hit dice. This is really hard to judge the value of.

My suggestion is that you sit down with your GM, look at the the Advanced Races play-test, and build a 10 point race that feels like a doppelganger to you.

You could also look at the Ebberon changeling for a low-power shapeshifter.