
Meirril |
That sort of assumes there is such a thing as an 'average' level 20. Most players never march a character from level 1 to 20. And a lot of the ones that do couldn't remember every little encounter between here and there.
I do remember how many kills this one cleric had is 4th edition D&D. 30th level epic cleric with zero kills. Pacifism has its perks, and that cleric could take you from negative hit points to full. He was kind of like a Godfather mobster figure. He never killed anyone, but he'd always point out a guy and say things like 'Its a real shame what you have done to me. If god forbid something were to happen to this dragon over here that fate has frowned upon someone might regain 30 hit points.'
Apparently pacifism means you can't damage someone, but it doesn't mean you can't set them up for someone else to wreck them.

Cevah |

In 3.5, it took an average of 13 encounters to level. Average encounter was CR=APL. Total number of encounters to get to level 20 is 13*19*X. So, 247X. I estimate X to ba about 1, as a boss encounter has fewer, but minion encounters have more. If I had to lean, I would say 1.25. So call it anywhere from 250-300. I don't think PF would be too different, but it might be fewer encounters per level. I don't think I have seen anything giving info to evaluate it.
/cevah

Grandis |

Depends on a lot of factors, like how much exp your party is getting per monster encounter. If your party has stronger gear, or is specialized for combat, you could be sending stronger monsters at them, which would mean more exp. Also the exp track matters, but I'll assume your on the normal track. Probably close to 200.
Also worth mentioning is that not all encounters are fully rewarding, some can give higher exp if you fulfill the right conditions, E.G. "Exorcise the vile demon from the poor sap it's possessed instead of just killing him" for more exp.