First of all I know how a refractometer normally works, take a OG before you pitch the yeast, write it down. Assuming the wine ferments out dry the OG can be used to know the final ABV, but if you take an FG with the refractometer rather than a hydrometer the reading will be off because of the alcohol. I know calculations can be made to correct the reading and get it to match the hydrometer. I am wondering if the same calculations could be made to determine the ABV of a dry wine that you did not take an OG of. obviously it would not work on a sweet wine but I am thinking on a dry wine it could work. See where I am going with this??? Any on have the calculation info??