Originally Posted by BNVince
Man, that online calculator says I should use a little more then a 1/2 gallon for a starter. That's pretty big.
Just remember that these are theoretical 'optimum' sizes. In practice, you can often do as well or nearly as well with somewhat smaller starters.
Regardless, the first purpose of the starter is to ensure the vitality of your yeast. The secondary purpose might be to propagate the yeast for a higher-gravity beer (hence the larger starter sizes). But if you oxygenate your starters really well, the yeast can perform a lot/all of the necessary propagation in your brew for most beers.