Brix to SG Converter

Brix measures dissolved sugar as a percentage by weight, treating the solution as if the dissolved solids were pure sucrose. Specific gravity measures density against water, with water defined as exactly 1.000. The formula above is the standard polynomial relation used across brewing and winemaking, fitted to real sucrose solution data rather than a simple straight-line approximation.

The relationship curves rather than running straight because a sugar solution's density doesn't scale perfectly linearly with sugar content. At low Brix the two scales track almost proportionally, but the curve bends more noticeably at the higher concentrations common in wine must, which is why a cubic-style polynomial gives a much closer fit than a single conversion factor.

If you are reading Brix on a refractometer after fermentation has started, the alcohol present will skew the result, since a refractometer measures light refraction and alcohol bends light differently than the sugar it's calibrated for. In that case use the refractometer tool, which applies the alcohol correction before reporting SG and ABV.

Brix is the standard sugar measurement throughout grape growing, tracked in the vineyard well before harvest to time picking and predict the eventual ABV. A grower checking Brix in the field with a handheld refractometer and a winemaker checking specific gravity with a hydrometer in the cellar are reading the same underlying sugar content through two different instruments and two different regional conventions.

Once you know your must's Brix or SG, the same reading feeds directly into predicting potential ABV, deciding whether to chaptalize, and planning nutrient additions, since all of those depend on how much fermentable sugar the must actually contains going into fermentation.