You can use these calculators to calculate the ABV, ABW and gravity of beer during/after fermentation.

Brewheads.com - Find ABW & ABV from final SG and Final Brix
This calculator will tell you the ABV and ABW of a beer from a refractometer and hydrometer reading after fermentation.

Brewheads.com - Find Gravity During Fermentation with Refractometer
This calculator tells you the gravity of your beer during/after fermentation from the current refractometer reading, and one from before fermentation began.