This tool allows you to convert between brix and gravity and calculates alcohol by volume (ABV) as well as alcohol by weight (ABV).

Formula:

ABV = (OG - FG) × 131
ABW = ABV × 0.79336 
GRAVITY = BRIX ÷ (258.6 - (BRIX ÷ 258.2 × 227.1))) + 1 
BRIX = (((182.4601 × GRAVITY - 775.6821) × GRAVITY + 1262.7794) × GRAVITY - 669.5622)