Sulfur dioxide (SO2) is the backbone preservative of home and commercial winemaking, guarding against oxidation, bacterial spoilage, and unwanted wild yeast activity. This calculator converts a target free SO2 level into the exact grams of potassium metabisulfite (KMeta) needed for your batch, so additions at crush, racking, and bottling stay consistent and measured rather than guessed.
How the Wine SO2 Addition Calculator works
KMeta mass = (target − measured current free SO2) × liters × 0.001 / 0.57. This is a theoretical starting addition, not an assured measured free-SO2 endpoint: binding and losses change the response. Use a current measurement, mix, allow appropriate equilibration and retest. The target table uses the selected volume, starts at zero and doses to the low end of each range. Free SO2 comprises molecular SO2, bisulfite and sulfite; bound SO2 is separate. Molecular SO2 has an antimicrobial role, while bisulfite contributes antioxidant protection. pH affects the molecular fraction; choose process-appropriate targets and verify analytically, rather than adding an unspecified extra amount.
Inputs and what they mean
KMeta mass = (target − measured current free SO2) × liters × 0.001 / 0.57. This is a theoretical starting addition, not an assured measured free-SO2 endpoint: binding and losses change the response. Use a current measurement, mix, allow appropriate equilibration and retest. The target table uses the selected volume, starts at zero and doses to the low end of each range. Free SO2 comprises molecular SO2, bisulfite and sulfite; bound SO2 is separate. Molecular SO2 has an antimicrobial role, while bisulfite contributes antioxidant protection. pH affects the molecular fraction; choose process-appropriate targets and verify analytically, rather than adding an unspecified extra amount.
Limits and edge cases
KMeta mass = (target − measured current free SO2) × liters × 0.001 / 0.57. This is a theoretical starting addition, not an assured measured free-SO2 endpoint: binding and losses change the response. Use a current measurement, mix, allow appropriate equilibration and retest. The target table uses the selected volume, starts at zero and doses to the low end of each range. Free SO2 comprises molecular SO2, bisulfite and sulfite; bound SO2 is separate. Molecular SO2 has an antimicrobial role, while bisulfite contributes antioxidant protection. pH affects the molecular fraction; choose process-appropriate targets and verify analytically, rather than adding an unspecified extra amount.