Wine Calculator

This wine calculator combines five winemaking calculations that cover a batch from must analysis through final blending: sugar and ABV conversion, chaptalization, sulfite additions, acid adjustment, and blending. Inputs accept decimal numbers and fractions such as 3/4 or 5 1/2, and results update automatically as values change.

Sugar and ABV converts a single reading between the Brix, Specific Gravity, and Plato scales and estimates potential alcohol by volume from it. The conversion uses the standard polynomial relationship SG = 1 + (Brix / (258.6 - (Brix * 227.1 / 258.2))). Potential ABV is estimated as (OG - FG) * 131.25, with FG assumed to be 0.990 for a dry fermentation.

Chaptalization calculates the sugar addition needed to raise a must from a current Brix reading to a target Brix, using either table sugar (sucrose) or honey. The weight needed is sugar (grams) = volume (liters) * (target Brix - current Brix) * density * 10, adjusted by a sugar type factor: 1.0 for sucrose, 1.25 for honey, since honey is only about 80 percent fermentable sugar by weight.

Sulfite / SO2 determines the potassium metabisulfite (K-meta) or Campden tablet addition needed to move free SO2 from a current level to a target level, in ppm, at a given wine pH. The amount needed is mg K-meta = volume (liters) * (target SO2 - current SO2) / 0.5725, where 0.5725 accounts for K-meta being 57.25 percent SO2 by weight. Campden tablets are treated as equivalent to 0.44 grams of K-meta each.

Acid Adjustment calculates how much tartaric, citric, or malic acid to add to move titratable acidity (TA), in grams per liter, from a current value to a target value: acid (grams) = volume (liters) * (target TA - current TA). The three acid types produce different flavor profiles, so the choice depends on the wine style being made.

Blending estimates the properties of a combined batch from the volume, ABV, TA, and pH of two source wines. ABV and TA are combined as weighted averages; pH is combined as an approximate weighted average, since pH blending is nonlinear in practice and the result is only an estimate.

Settings holds the number of decimal places displayed and a step-by-step formula breakdown for each of the five calculations.

This calculator addresses the most common measurements and adjustments encountered during home winemaking, from initial must analysis through final blending. Each mode targets a specific stage of the process.

• Harvest Assessment: Measure grape must at harvest with a refractometer reading of 23.5 Brix and see the equivalent Specific Gravity of 1.099 and a potential ABV of approximately 14.3 percent. Compare readings across multiple grape lots to decide which to blend or ferment separately.
• Must Correction: A cool-climate Riesling must reading 18 Brix needs about 1,290 grams (1.29 kilograms) of table sugar per 20 liters to reach 24 Brix, a potential ABV of about 14.6 percent. Plan sugar additions before fermentation begins.
• Sulfite Management: Add the correct amount of potassium metabisulfite after malolactic fermentation. A current free SO2 of 5 ppm and a target of 35 ppm at pH 3.4 calls for approximately 1.05 grams of K-meta, or about 2.4 Campden tablets, across a 20-liter batch.
• Acid Balancing: Adjust a flat-tasting Merlot with a TA of 4.5 g/L up to 6.5 g/L by adding 40 grams of tartaric acid to a 20-liter batch. Compare the amounts needed if using citric or malic acid instead.
• Blending Trials: A 60/40 blend of a high-acid Cabernet (TA 7.0 g/L, ABV 14%) with a softer Merlot (TA 5.5 g/L, ABV 12%) predicts the blended result before committing to the full batch. Adjust the ratio until the target profile is reached.
• Education: Study the relationships between Brix, Specific Gravity, and Plato scales side by side, using the step-by-step formula display to follow each conversion and understand the underlying math.