Help with yeast calculation

[Quin]

Regarding the 1.63L starter:

The 1.63L starter is the exact size needed to hit 0.75 million cells per mL pitching rate. It's best if you can pitch an active starter so pitch the whole thing into your wort especially for an ale. A 2L starter would be fine also.

I doubt you would would be getting into overpitching unless you were using the entire yeast slurry from a previous batch into a small beer.

If your fermentations are going to terminal gravity, you could try backing down on the pitch rate by 10% per iteration until you are getting the flavor you want.

[adamK]

I have a question, mostly related to the fact that I've never used a flask; all my starters are done in growlers, 1g 'growler' jugs & 3g carboys. Can you seriously do a 2L starter in a 2L flask? I know the 2L mark isn't at the top, but there still isn't what I would consider adequate headspace above that 2L mark.

You can, if you use fermcap-S to control boil over and krausen.

[spiderwrangler]

I have a question, mostly related to the fact that I've never used a flask; all my starters are done in growlers, 1g 'growler' jugs & 3g carboys. Can you seriously do a 2L starter in a 2L flask? I know the 2L mark isn't at the top, but there still isn't what I would consider adequate headspace above that 2L mark.

You can, if you use fermcap-S to control boil over and krausen.

I do mine on a stir plate covered in foil, I feel like the gentle vortexing likely reduces foam build up too, but I do use an anti-foam agent.