Brix to Potential Alcohol Calculator

Brix (°Bx) measures the percentage of dissolved sugar in grape juice by weight. It is the number that decides harvest day, and it is the one measurement that predicts, before a single yeast cell goes in, roughly what the finished wine will be.

Conversion formula: Potential ABV ≈ Brix × 0.55 to 0.59

The factor is a range rather than a constant because yeast is not a machine. Some of the sugar becomes cell walls and glycerol rather than ethanol, some alcohol evaporates through the airlock, and different strains differ by a percent or two. The chemistry sets a ceiling of about 0.607 if every sugar molecule converted perfectly. 0.55 is the conservative choice and the one to plan a wine around, 0.57 is typical, and 0.59 flatters your yeast.

Harvest timing by Brix:

• Under 20 °Bx: too early, giving low alcohol, hard acidity, and green under-ripe flavours
• 20 to 22 °Bx: early-harvest style, crisp whites and sparkling base wine
• 22 to 24 °Bx: ideal for most white wines, landing near 12 to 14% ABV
• 24 to 26 °Bx: ideal for most reds, landing near 13 to 15%
• 26 to 28 °Bx: rich, full-bodied style, with a real risk of stuck fermentation unless you feed the yeast properly
• Over 28 °Bx: dessert territory, and unlikely to ferment dry at all

Sugar is only one of three ripeness clocks, and it is the fastest. Phenolic ripeness (soft seeds, supple tannin) and flavour ripeness run on their own schedules, and in a hot year Brix races ahead of both. That is how you end up with a 15% wine that still tastes green. Chew a few seeds and taste the skins before you trust the refractometer.

Measurement tools: a refractometer takes one drop of juice and reads instantly, which is why it lives in the vineyard. A hydrometer needs a full sample tube but does not care about alcohol, which is why it lives in the cellar. A refractometer is only honest before fermentation starts. Once alcohol is present it bends the light far more than sugar does and the reading is meaningless without a correction formula.

Potential vs actual alcohol: this is potential alcohol, which assumes the yeast finishes the job. Sweet wines keep some sugar back on purpose, and a stuck fermentation keeps it back against your wishes. Either way the wine ends up weaker than the number here.