The “Econo Hydrometer” measures liquid density or specific gravity (S.G) to monitor fermentation and sugar levels. As a general rule an active wine will ferment -.010 S.G per day, thus providing a visual indication of fermentation.
To determining the alcohol content use the alcohol scale on the hydrometer. Take one reading before fermentation. Take the final reading after fermentation is complete. E.g.
Original Reading: 11% S.G. 1.085
Final Reading: (+)-1% S.G 12% 0.992
The difference between the first and last reading gives you the percentage of alcohol in your wine, e.g. First reading is 11% (S.G – 1.085). Final reading is minus 1% (S.G – 0.992). The difference between these readings is 12%, which means your wine is 12% alcohol by volume.