How many of you thought that you could toss your hydrometer in the trash when you bought a refractometer? Well, actually you can retire your hydrometer and use your refractometer to measure final gravity if you use this handy calculator. Since alcohol is less dense than water, a refractometer won’t accurately measure specific gravity after the yeast have done their work. This calculator corrects the reading for you so you don’t have to waste wort in a test jar or waste time sanitizing a beer thief. It is accurate and works with brix refractometers and specific gravity units as well.
http://seanterrill.com/2012/01/06/refractometer-calculator/
American Homebrewers Association
Hopheads 