How do you obtain the stats for monsters in pathfinder? (For custom encounters)

[MonkeySage]

I want to create custom encounters, like say an ogre with levels of barbarian as an example... How do I obtain the stats for an ogre to add class levels to it? Things like ability scores and such.

3.5 it was so easy to add class levels to almost anything, but pathfinder seems to have made things difficult in this department.

[Yanisa]

I'm pretty sure that between 3.5 and Pathfinder monster building hasn't changed a lot.

There is a lot of stuff in the Monster Entry Format and the chapter on Monster Advancement. I never bothered to read it all and general use my 3.5 knowledge.

But on the subject of

Ability Scores

The creature's ability scores are listed here. Unless otherwise indicated, a creature's ability scores represent the baseline of its racial modifiers applied to scores of 10 or 11. Creatures with NPC class levels have stats in the standard array (13, 12, 11, 10, 9, 8), while creatures with character class levels have the elite array (15, 14, 12, 11, 10, 8); in both cases, the creature's ability score modifiers are listed at the end of its description. Ability scores are capitalized and their names are listed in bold.

So your barbarian ogre would get +4, +4, +2, +2, +0, and –2 to its stats. (That's the difference between six times 10 and the elite array). You could also calculate his racial modifier by subtracting 10 or 11 like 3.5 and then give it whatever base ability scores your want.

[BWR]

3.5 it was so easy to add class levels to almost anything, but pathfinder seems to have made things difficult in this department.

Huh? You do exactly the same thing as you did in 3.5. There is not one whit of difference. How did you come to believe it was different?

[Svm420]

I use this site with great success for when I don't feel like doing all the work myself. But if you're perfectionist make sure to doublecheck numbers.