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Wine Sulfite Calculator

Calculate SO2 and potassium metabisulfite additions for winemaking. Free and total sulfur dioxide dosing by pH and volume.

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Inputs that matter
Wine Volume, Current Free SO₂, Target Free SO₂, pH
Output to expect
Wine SO₂ Dosing Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

KMBS to SO2

Potassium metabisulfite is 57% SO2 by weight. 1 g in 1 liter adds ~570 ppm SO2 (before binding).

1 g KMBS releases ~570 mg SO2

Free SO2 Target by pH

At pH 3.2: 25 ppm free SO2 adequate. At pH 3.6: need 50 ppm. At pH 3.8: need 75+ ppm for same antimicrobial protection.

Target free SO2 increases with pH (molecular SO2 constant)

Addition Calculation

Calculate ppm deficit, multiply by volume, divide by SO2 yield per gram KMBS.

KMBS (g) = (Target − Current) ppm × Volume (L) ÷ 570

Updated: July 2026

Example Scenarios

pH 3.5, current free SO2 15 ppm, target 35 ppm: need 20 ppm addition → 0.7 g KMBS for the batch.

50 ppm SO2 on 100 kg crushed grapes (~75L juice): 6.6 g KMBS added at crush for antimicrobial protection.

One tablet ≈ 0.44 g KMBS ≈ 250 ppm SO2 per gallon. Calculate tablet count from KMBS gram equivalent.

FAQ

Depends on pH. General range: 20–35 ppm for red wines, 25–45 ppm for whites. Higher pH requires more free SO2 for equivalent protection.

Free SO2 is unbound and active for protection. Total includes bound SO2 (reversible). Only free SO2 matters for antimicrobial and antioxidant effect.

At crush, after malolactic fermentation, at each racking, and at bottling. Test free SO2 every 2–3 months during aging.

Aeration-oxidation method (most accurate), Aspiration method, or commercial test kits (Chemetrics, Vinmetrica). Electronic meters available for quick checks.

Yes. Excess SO2 causes nasal/throat burn, masks fruit character, and exceeds TTB legal limits (350 ppm total SO2). Always calculate additions carefully.

About Wine Sulfite Calculator

Sulfur dioxide (SO2) protects wine from oxidation and microbial spoilage. Enter wine volume, current and target free SO2, pH, and product concentration to calculate potassium metabisulfite (KMBS) or Campden tablet additions.