Correcting refractometer reading during fermentation

A refractometer does a great job of identifying initial sugar (Brix) levels of a must before fermentation, using just a drop or two of liquid. Once fermentation starts, however, the measurements get confused because of the way in which alcohol changes the refraction. To correct for changes in alcohol level and still use your refractometer, Keystone Homebrew has created a very handy calculator, linked below:

http://www.keystonehomebrew.com/RefractCalc_1A.xls