Basic facts:

1 litre of water weighs 1 kg (1.000 grammes)

1 litre of alcohol weighs 0,8 kg (800 grammes)

1 litre dissolved sugar weighs 1,59 kg

When the must begins fermentation the sugar content is high. The hydrometer (with Oechslescale) reading is then about +80 degrees. As the sugar ferments to alcohol the reading gets lower and lower.

Measure the gravity of the must at the start of fermentation.

Refer to the table "When the wine has fermented out" to see what the hydrometer (with Oechslescale)  reading should be.

Measure the wine during fermentation.

By seeing where the reading stands between the start value and final value you can see how far fermentation has progressed.

+80º Oechsle

+40º Oechsle

0º Oechsle