Sulfur in Wine Calculator

About the Sulfur in Wine Calculator

Sulfite (SO₂) is one of the main tools winemakers use to limit oxidation and microbial spoilage. The challenge is dosing enough to protect the wine without overshooting the target free SO₂ level.

This calculator converts between common sulfite-addition forms such as potassium metabisulfite powder and Campden tablets. Enter the batch volume, current free SO₂, target level, and wine pH, and the page estimates the addition needed to move from the current level to the target.

Because the protective molecular SO₂ fraction changes with pH, the same free SO₂ reading can mean very different protection levels in two wines. That is why the pH-based context matters when you choose a sulfite target.

When This Page Helps

Sulfite additions are one of those cellar calculations where small arithmetic errors matter. The required addition depends on batch size, current free SO₂, target protection level, and pH, so doing it casually in your head is an easy way to underprotect or overshoot a wine.

How to Use the Inputs

1. Enter your wine volume (gallons or liters)
2. Enter current free SO₂ level (from testing)
3. Set target free SO₂ (or use pH-based recommendation)
4. Enter your wine's pH for optimized recommendations
5. View K₂S₂O₅ and Campden tablet amounts
6. Reference the timing guide for when to add

Example Calculation

Tips & Best Practices

• Always dissolve K₂S₂O₅ powder in a small amount of water or wine before adding — never add dry powder directly
• Measure with a milligram-precision scale — even 0.1g makes a difference in small batches
• Test free SO₂ before every addition — don't just add on a schedule without testing
• Higher pH wines lose SO₂ faster and need more frequent checks
• Crush and dissolve Campden tablets fully — undissolved pieces create localized high-concentration zones
• Add SO₂ after MLF is complete, not before, to avoid stuck malolactic fermentation

pH and Sulfite Effectiveness

At pH 3.0, about 6% of free SO₂ is in molecular form. At pH 3.5, only 1.5% is molecular. At pH 3.8, just 0.6%. This means a pH 3.8 wine needs 4× more free SO₂ than a pH 3.2 wine to achieve the same protection. Always factor in pH.

When to Add SO₂

Key addition points: (1) at crush to suppress wild yeast, (2) after fermentation completes, (3) after MLF completes, (4) at every racking, (5) before bottling. Each addition should bring free SO₂ to the target for the wine's pH.

Organic and "No Sulfite" Wines

All fermentation produces some SO₂ naturally (5–20 ppm). "No sulfite added" wines still contain sulfites. Wines without adequate SO₂ protection have shorter shelf lives and are more prone to oxidation and microbial spoilage. Most winemakers consider SO₂ management the single most important aspect of wine quality.

Frequently Asked Questions

• What's the difference between free, bound, and total SO₂?

  Free SO₂ is the active protective form. Bound SO₂ has reacted with wine compounds and is no longer protective. Total SO₂ = free + bound. Only free SO₂ matters for protection.

• How much SO₂ should wine have?

  White wines: 25–50 ppm free SO₂. Red wines: 20–40 ppm. Sweet wines: 50–70 ppm. The exact target depends on pH — higher pH needs more free SO₂ to maintain adequate molecular SO₂.

• What is molecular SO₂?

  Molecular SO₂ is the truly antimicrobial fraction of free SO₂. At wine pH, only 1–6% of free SO₂ is in molecular form. Target: 0.6–0.8 ppm molecular SO₂.

• How often should I test SO₂?

  At every racking, before and after MLF, before bottling, and monthly during aging. Free SO₂ declines over time as it binds to compounds in the wine.

• Can you taste sulfites in wine?

  Most people can detect SO₂ above 40–50 ppm. Sensitive individuals may notice it at 20 ppm. The legal maximum is 350 ppm in the US, but good wines rarely exceed 100 ppm total.

• Is one Campden tablet the same as K₂S₂O₅ powder?

  One standard Campden tablet contains 75mg K₂S₂O₅, which releases ~50mg SO₂. In 1 gallon, this adds ~50 ppm free SO₂. For precise dosing, weigh powder on a milligram scale.