Wine SO₂ PPM Calculator
Sulfites protect wine from oxidation and microbes, but too much ruins aroma. Winemakers target 30–50 PPM free SO₂ — and potassium metabisulfite is only 57% SO₂, which this calculator accounts for.
Calculator
Wine SO₂ PPM Calculator
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Sulfites protect wine from oxidation and microbes, but too much ruins aroma. Winemakers target 30–50 PPM free SO₂ — and potassium metabisulfite is only 57% SO₂, which this calculator accounts for.
How to use this calculator
- Enter wine volume.
- Enter target free SO₂ (30–50).
- Get grams of KMS.
- Stir gently, re-test.
The formula
KMS is ~57% SO₂ by weight: grams = target PPM × liters ÷ 1,000 ÷ 0.57.
What the inputs mean
The target is the concentration you want, in PPM. The volume is how much liquid you are treating. The so₂ content of kms (%) corrects for product strength, because most products are not 100% active ingredient. The result tells you exactly how much potassium metabisulfite to add.
Worked example
100 L at 40 PPM: 40 × 100 ÷ 1,000 ÷ 0.57 ≈ 7 g KMS.
Quick reference
| Wine volume | KMS for 40 PPM |
|---|---|
| 20 L | 1.4 g |
| 100 L | 7 g |
| 500 L | 35 g |
From zero free SO₂; measure current first.
Where you will actually use this
The 57% factor is the step everyone forgets.
- Home winemaking
- Commercial cellars
- Post-fermentation protection
Mistakes that give wrong answers
- Dosing for total instead of free SO₂
- Ignoring pH (molecular SO₂ depends on it)
Key takeaways
- Formula: KMS (g) = Target SO₂ PPM × Wine (L) ÷ 1,000 ÷ 0.57
- Remember: From zero free SO₂; measure current first.
- Watch out for: Dosing for total instead of free SO₂
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
How much SO₂ in wine?
Typically 30–50 PPM free SO₂; legal total limits ~150–200.
What is KMS?
Potassium metabisulfite — the standard sulfite source, 57% SO₂.