There's also a spreadsheet available from a number of sources that will help with the conversion/adjustment once fermentation has started. Rebel Brewer has one (a web page actually), I think I've seen the same thing posted on other stores, but can't locate them right now. I also believe there's another one somewhere in the threads on HBT (haven't looked yet).
You'll want to use the brix reading on the spreadsheet. At first, I was annoyed by this since my first refractometer was SG and brix. But, I just recently picked up some more refractometers (two that go to either 32 brix, with a .2 resolution, and another to 20 brix with a .1 resolution) which makes it easier. I also have one that goes to either 60 or 62 brix (starts at 20 brix I believe), for testing other things.
I used the spreadsheet for recent batches and it converted to a good number. It was actually the estimated FG from BeerSmith.
I think they must have updated the formula used in the spreadsheet since the podcast mentioned earlier. I'll also be running the numbers through BeerSmith to see how that works out. I really like how little a sample you need for refractometer readings. Since I give my batches enough time to finish, I'm just looking to see what the FG is, so that I can get the ABV% number