Fermentation Basics
Brix vs Specific Gravity
Compare two common ways of describing dissolved extract and learn when a conversion is only an estimate.
Two scales, related measurements
Degrees Brix expresses sucrose-equivalent soluble solids by mass. Specific gravity compares density with water. For an unfermented sucrose solution, a Brix reading can be converted approximately to SG.
Fruit juice and wort contain more than sucrose. Their refractive index and density reflect a mixture of dissolved substances, so converted values are operational estimates rather than exact sugar analyses.
Choose the right instrument
Refractometers need a small sample and are convenient for tracking original extract. Hydrometers measure density directly and remain useful after fermentation, provided temperature is considered.
Alcohol changes the refractive index. For a fermented sample, do not treat raw refractometer Brix as final gravity; use a validated correction based on the original reading or take a hydrometer measurement.
Keep readings comparable
Record which instrument and scale you used, along with temperature. Use the same method throughout a batch whenever practical.
For critical production or labeling decisions, use an appropriate calibrated instrument or laboratory analysis rather than relying on a simple conversion.