How much yeast for small batches?

[Joe_in_GA]

I'm thinking about making a few small batches, 1-2.5 gals each, to try out some recipes. I plan on harvesting some ale yeast from my next 5 gal batch and using that. How can I figure out how much to use? Should I just use full jars, or should I use part of the yeast and save or toss the rest?

On a related note, when harvesting the yeast how small can the jars be and still be effective for a 5 gal batch?

Thanks guys.

 

[TipsyDragon]

go here. it gives guide lines on estimating your pitch rate and figuring out how many yeast packets you need.

beer math

 

[HomerJR]

Or you could use Mr. Malty's pitching rate calculator.

 

[magnj]

I regularly do 2.5-3 gallon batches and I usually do a smack pack or jar of washed yeast + a 2-4 cup starter. The calculators are nice to get you in the right area too.