Question about Craftmanship and progress

Is there a way to determine how much progress I will make on a certain item with say, Careful Synthesis? Or another way to ask, if I wanted to find out how much more craftmanship I need to be able to complete an item with 2 careful synthesis casts, how would I do that?

Edit(Since I can't post another topic)-
Off topic, but I have a similar question about Gathering and chance to actually gather something from a node with botany/mining. Is there a way to determine how much Gathering I would need to be able to gather something 90-100% of the time?

I haven't seen anyone work out any formulas yet (and once you get lv50 with good gear, it hardly matters), so the best anyone can offer you is to just try it out and see.