In brewing and fermentation, specific gravity is a measurement used for the density, or weight, of a liquid compared to water. Simply put, specific gravity tells us the weight of a liquid compared to water. And in fermentation, the additional weight in the water is mostly dissolved sugar.
Specific Gravity is a standard scale or measurement used in brewing and winemaking; other scales include Brix, Plato, and Potential ABV. No matter which scale you use, they provide the same information in different formats, much like a thermometer that reads in Celsius and Fahrenheit. The temperature remains the same, but it’s shown in two different scales.