The following illustrates the versatility of the hydrometer
(with specific gravity scale).

A hydrometer usually looks like this

But one could also look like this

1 kg dissolved sugar has a volume of 0,63 litres

1 litre of alcohol weighs 0,8 kg

2,7 grammes gives 1 hydrometer degrees in 1 litre of water

Fermented hydrometer degrees divided by 8 = % volume of alcohol.

A finished wine must have a certain hydrometer reading to be
balanced (refer to table)

17 grammes of sugar ferments to 1% alcohol in 1 litre of wine

The hydrometer reading -1000 x 2 = grammes of sugar in fruit juice

Strong wine yeast only tolerates 16-18% alcohol
(table wine 13%), after which fermentation ceases