Is it possible to over pitch?

Just picked up a 3 gallon carboy that I would like to use for experimental batches and such. Since most yeast packs are enough for 5 gallons can I still use a normal yeast pack for a 3 gallon batch instead of a 5 gallon batch?

 

Yes it is possible to overpitch, check mrmalty.com for proper rates. Depending on your experimental batch OG, however, 1 packet (liquid yeast?) should be fine.

 

I normally use liquid yeast so this makes me feel better. But I will check out mrmalty too.

 

It takes orders of magnitude more yeast to overpitch and notice any effect than underpitching by just a little bit having a noticeable effect. For 3 gallon batches you still will probably need to step up yeast packs with a starter. No need to worry about overpitching, worry more about underpitching.

 

It also depends on OG of wort.
Dry yeast usually have 200B cells which is plenty enough to ferment 5 gal of 1.054 wort, if we are brewing 3 gal we will over pitch it almost by double. But if we brew 3 gal of RIS with 1.100 OG it will be right pitching rate.