League of Legends (LoL) Question: What is a healthy farm?

More than who you're laning against (as a minimum).

180 by 20 is what you should be aiming for as a nearly perfect amount.

220+ by 20 if you're Karthus.

Calculating time :D

Data
Each 0,5 minute, a minion wave spawns.
The amount of total minutes = 20
Each minion wave has a minimum of 6 minions.
1 bonus minion (siege minion) will appear every 3 waves.
The first 1,5 minute, there are no minion waves.
The first 2,5 minutes will have no bonus minion

Calculation
Minimum minions
Since the first 1,5 minute does not spawn any minions, we will say that the timer is 18,5.
In those 18,5 minutes, the amount of minion waves is:
18,5*2 = 37 minion waves.

The amount of minions that would be is:
37*6 = 222 minions at 20 minutes

Bonus minions
The first 2,5 minute, there is no bonus minion spawning, from there on, every 1,5 minute 1 bonus minion appears. So that means the timer is 17,5 minutes for starters.
In those 17,5 minutes, the amount of bonus minions is:
17,5/1,5 = 11,6666667 ~ 12 minions.

That means in total, at 20 minutes you would have 12+222 = 234 minions in 1 lane.


Grading
Back to school, let's grade your farm.
If you have a grade below 6, you failed! :O
A 6 equals: 234 * 0,6 = 140 minions at 20 minutes

But of course, a 6 is the minimal, let's boost it up to an 8! :O
234 * 0,8 = 187,2 minions at 20 minutes.

That's more like it! :D
What grade do YOU want to get? :D


Conclusion
You should have a minimal (really a minimal) of 140 or else you have failed :O

Rule of thumb is 100 by 12 minutes, 200 by 20 and 300 by 30. The first milestone is the most important to focus on, the others will follow easily then.

As a rule of thumb I use the following:

- 150 CS by 20 minutes.
- 200 CS by 300 minutes.
- Endgame should be no less than 300 minions.

CSing as a jungler takes a whole new world of considerations. You should be more focused in having levels rather than CS. It's not uncommon to have 80 CS as a jungler by 30 minutes and that doesn't mean you suck.

Counter-jungle oriented champions however should have more demanding goals and CSing is more important to them as it gives a notion of how much they've denied.

- 150 CS by 30 minutes as Shyvana is what I consider to be a good job with her.

For every lane: 10 CS per minute after 2:00, subtract 10 for every successful gank you pull off. Lower CS acceptable if sieging or forcing baron/dragon, as what matters is relative CS and not absolute CS.

I use 185 as my 20 minute mark goal for midlane. It's just short of 80% of the creeps and means you've missed a bit over 1000g out of 5109g. That said, 185 is my goal. Healthy might reasonably be a little less than that.

Based on MY experience your CS should look like that:

Jungler: depends on your ganks but I think at least 70-90
Support: 0 XD
APC and ADC: at least 150+ kills
Top: Not sure because Top is the only lane I dont play often^^