Yep the bigger the starter the higher the cell yield. I use a chart in one of my books "How To Brew". To basically give you an idea a 1.060 OG brew needs about 230 billion cells. Wyeast or White Labs liquids have about 80-100 billion when you buy them. My chart says that with 100 billion in a 1 qt starter = 168 billion. 100 billion in a 2 qt starter = 226 billion. and so on...... You could also begin with a 1 qt starter and then pitch that into a fresh 1 qt starter to increase count.
I started by using Mr Malty calculator on the internet but have since been using my book and a chart I made up. Once you get a rough idea you are good to go. I usually try to get close and in the past have heard bad things about over pitching yeast but have also read that you have to dramatically over pitch to get any bad results from it.
Next Brew: Cascades Orange Pale Ale
Primary: Indus IPA
Secondary: Belhaven 80 Shilling
Carbing Up: Simply Hefe
On Tap: Fat Tire, Watneys Cream Stout, Bombshell Blonde