Ckujawa - Once you get in the habit of using the refractometer on fermenting wort and running the numbers in a calculator to make the appropriate conversion, you'll be glad you have it. I use the tool built into beersmith2 and it is very straightforward. Different calculators use somewhat different functions to make the gravity conversion, so it is always an estimate, but I find the refractometer much more convenient than a hydrometer. Also, they are significantly less fragile!