SO₂ Wine Calculator
Adjust sulfite additions accurately to protect your wine from oxidation and spoilage.
Target should exceed current reading.
SO₂ increase needed
20.0 ppm
Potassium metabisulfite
0.67 g
≈ 1.52 Campden tablets
Wine volume (L)
19.0 L
5.02 gal
How to Use This Calculator
Measure current free SO₂
Use an aeration-oxidation kit or digital SO₂ meter to capture the present free sulfur dioxide level.
Choose a target based on pH and style
Consult sulfite tables—higher pH wines need higher free SO₂ to protect against microbes and oxidation.
Weigh and dissolve K-meta
Mix the calculated potassium metabisulfite in a small portion of wine or water, then gently stir into the batch.
Formula
K-meta grams = (Δppm × Volume(L)) ÷ 570
Campden tablets = grams ÷ 0.44
Example: 5 gal (18.9 L) wine from 20 ppm to 35 ppm → (15 × 18.9) ÷ 570 = 0.50 g K-meta ≈ 1.1 tablets.
Reminder: Potassium metabisulfite is ~57% SO₂ by weight.
Full Description
Sulfur dioxide (SO₂) is a critical antioxidant and antimicrobial agent in winemaking. Maintaining adequate free SO₂ helps prevent oxidation, browning, and microbial spoilage. This calculator determines how much potassium metabisulfite (K-meta) you need to achieve a desired increase in free SO₂ for any batch size.
Enter your wine volume, current SO₂ measurement, and target SO₂. The results show grams of K-meta to weigh and an equivalent number of Campden tablets for convenience. Dissolve the preservative before adding to ensure even distribution and avoid localized hot spots.
Why SO₂ management matters
- Protects against oxygen pickup during racking and bottling.
- Inhibits wild yeasts, bacteria, and Brettanomyces.
- Maintains aromatics and color, especially in white wines.
- Ensures stability for storage, shipping, and cellaring.
Always adjust based on wine pH: lower pH wines require less SO₂ for protection. Regularly retest free SO₂ levels, as sulfur dioxide binds with aldehydes and other compounds over time.
Frequently Asked Questions
How often should I test SO₂?
Check monthly during bulk aging and before bottling. Wines with higher pH may need more frequent adjustments.
What about molecular SO₂?
Molecular SO₂ depends on pH. Consult tables to ensure your free SO₂ provides at least 0.8 ppm molecular SO₂ for whites and 0.5 ppm for reds.
Can I over-sulfite my wine?
Yes. Excess SO₂ can cause off-aromas and palate bite. Add in small increments and re-test after mixing.
Are Campden tablets the same as K-meta powder?
Campden tablets are pre-measured potassium metabisulfite doses. Each tablet is approximately 0.44 g.