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Winemaking Suite

Three common cellar calculations: the free SO₂ needed to hit a molecular-SO₂ target at your wine's pH, potential alcohol from must °Brix, and tartaric acid to raise titratable acidity.

How to use this tool

Three quick cellar calculations side by side: how much sulfite to add for microbial protection, how strong the finished wine will be, and how much acid to add to brighten a flat must.

What to enter

Free SO₂, Wine pH and Molecular SO₂ target (mg/L). Only the molecular form protects against microbes, and how much of your free SO₂ is molecular depends on pH; ~0.8 mg/L molecular is the usual table-wine benchmark.
Potential alcohol, Must sugar in °Brix (percent sugar). The tool estimates the alcohol that sugar will ferment to.
Acidity, Current TA and Target TA (g/L as tartaric). The gap is how much tartaric acid to add.

Reading the result

Each card returns one number: the free SO₂ to dose (mg/L) to reach your molecular target, the potential alcohol (%ABV), and the tartaric acid (g/L) to add. Adding acid lowers pH, which changes the SO₂ figure, re-check SO₂ after acidifying.

Worked example

At pH 3.4, hitting 0.8 mg/L molecular SO₂ needs ≈ 32 mg/L free SO₂; 24 °Brix must ferments to ≈ 13.2% ABV; raising TA from 5.0 to 6.5 g/L means adding 1.5 g/L tartaric.

Free SO₂ for molecular target

Wine pH

Sets how much of the free SO₂ is in the active molecular form, lower pH needs less free SO₂ for the same protection. Molecular SO₂ target mg/L

mg/L

~0.8 mg/L molecular SO₂ is the usual microbial-protection benchmark for table wine.

Potential alcohol from Brix

Must sugar °Brix

°Bx

Uses the common 0.55 %ABV per °Brix conversion factor.

Acidity adjustment

Current TA g/L tartaric

g/L

Target TA g/L tartaric

g/L

Methodology

Only molecular SO₂ is antimicrobially active, and its fraction of free SO₂ depends on pH (pK_a1 of sulfurous acid = 1.81): free SO₂ = molecular × (1 + 10^{pH − 1.81}). Potential alcohol uses 0.55 %ABV per °Brix. Tartaric addition to raise titratable acidity is the difference (target − current) in g/L, expressed as tartaric acid.

Known limits

The Brix → alcohol factor varies with yeast strain and must composition (0.50–0.60 %ABV/°Bx); treat the result as an estimate.
Adding tartaric acid lowers pH, which in turn raises the molecular-SO₂ fraction; re-check SO₂ after an acid addition.
Always confirm final SO₂ against your wine's legal limit for the style and region.