If yeast calculator calculations tell me I only need a half litre starter, can I use 2oz of DME, and 2 cups of water, and a whole pack of Wyeast yeast? or do I have to make it as a 1L starter, and only pitch about half?
You can always make a full size starter, then cold crash and decant the liquid. Take the yeast you need and pitch it, then save the rest for a future yeast starter. That way you don't have to buy more yeast and you don't have to try and wash yeast afterward. That's what I do, anyways.
That's what I'm thinking.. my concern is that I'll make the starter, and still manage to under pitch (that'd just be my luck) if I eye ball it.
This is all hypothetical right now. I only do 2.5gal all grain BIAB. I got away with just pitching a Wyeast 1056 last time without a starter (under pitched by about 15 billion cells, but it turned out fine). Went from 1.06 to 1.008 and the sample tasted fine. But I don't necessarily want to take that chance again. That yeast was a month old when I bought it.
I likely will do a 1L starter, decant and measure out what I think I need.