I use a refractometer to do all of my "specific gravity" fermentation measurements because it takes so little beer to do a measurement. The alcohol in solution makes the standard Brix to SG calcuation not work, as it changes the refraction index of the solution, but it is good enough to tell when the beer has fermented out. However, I'm always curious what the actual specific gravity is while performing these readings.
There are various sites that outline methods of estimating SG, if you know the starting Brix:
http://onebeer.net/refractometer.shtml
http://brew.stderr.net/refractometer.html
http://morebeer.com/view_product/18739/ ... Dual_Scale (Documents -> Refractometer Alcohol Correction Spreadsheet)
It would be pretty sweet it Brewer's Friend also had such a calculator... available from the Android app as well.
There are various sites that outline methods of estimating SG, if you know the starting Brix:
http://onebeer.net/refractometer.shtml
http://brew.stderr.net/refractometer.html
http://morebeer.com/view_product/18739/ ... Dual_Scale (Documents -> Refractometer Alcohol Correction Spreadsheet)
It would be pretty sweet it Brewer's Friend also had such a calculator... available from the Android app as well.