Sulfite Addition Calculator (Wine SO2)
Calculate potassium metabisulfite (K-Meta) or Campden tablet dose to achieve target free SO2 in wine.
Accounts for wine pH for accurate protection.
Sulfite (SO2) addition is the most critical chemical intervention in winemaking. Sulfur dioxide protects wine from oxidation and microbial spoilage, preserving color, aroma, and flavor.
The Formula:
SO2 to add (mg/L = ppm) = Target free SO2 − Current free SO2
Potassium Metabisulfite (KMS) needed (grams) = (SO2 ppm × Volume in liters) / 570
The factor 570 accounts for the fact that KMS is approximately 57% effective SO2 by weight.
Molecular SO2 (Active Protection):
The effective protective form is molecular SO2, which depends on pH:
| Wine pH | Free SO2 Needed for Protection |
|---|---|
| 3.0 | 6 mg/L |
| 3.2 | 10 mg/L |
| 3.4 | 16 mg/L |
| 3.6 | 26 mg/L |
| 3.8 | 40 mg/L |
Higher pH wines need dramatically more free SO2 to achieve the same protection.
Worked Example:
19-liter batch of Chardonnay, pH 3.4:
- Target free SO2: 30 mg/L
- Current free SO2: 8 mg/L
- SO2 deficit: 22 mg/L
KMS needed = (22 × 19) / 570 = 418 / 570 = 0.73 grams
Dissolve in 50 mL of wine or water, stir gently into the batch.
Addition Timing:
| Stage | Free SO2 Target |
|---|---|
| Crush/pressing | 50–75 mg/L (inhibit wild yeast) |
| Post-fermentation | 25–35 mg/L |
| Pre-bottling | 30–40 mg/L |
| Bottled wine (for aging) | 35–45 mg/L |
Practical Tips:
- Test free SO2 regularly with the Ripper method or AO2 test kit
- Never add SO2 during active fermentation — it kills yeast
- Always check local regulations — maximum legal SO2 levels vary by country (EU: 160 mg/L red, 210 mg/L white)