Degrees Brix (°Brix), named after the German chemist A. Brix, is a relative measure of the amount of sucrose in a solution. Generally speaking, 1 °Brix is equivalent to a water-based solution containing 1% sucrose by weight.
The Brix value is determined using a Refractometer. In short : this measurement is based on the determination of the critical angle of total reflection. When light moves between two different substances (e.g. air and water) it is refracted. The Brix value appears in the digital readout.