Fermentation Time Calculator

Sauerkraut, kimchi, kombucha, sourdough: time depends on temperature; Q10 rule applies.

Inputs

Result

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How to use this calculator

  • Pick ferment.
  • Enter your kitchen / fermentation temp.
  • Read window.
  • Taste at the start of the window; refrigerate when satisfied.

About this calculator

Lacto-fermentation (sauerkraut, kimchi, lacto-pickles) is driven by lactobacillus, which doubles roughly every 18°F. Yogurt is thermophilic — runs at 100-115°F to favor specific cultures. Kombucha SCOBY likes 72-78°F. The "is it done?" question always ends with taste — visual cues are unreliable. Acid production stops once pH drops below 4.6 (preserved indefinitely in fridge). Trust your nose: fermentation gone wrong smells distinctly off (rotting, ammonia) — toss it.

Frequently asked

How do I know it's "done"?+
Taste. Sauerkraut: tangy not vinegary, satisfying crunch. Kimchi: sour funk. Kombucha: lightly tart, no remaining sweetness if dry-style.
Mold on top?+
White kahm yeast: harmless, scrape off. Fuzzy black/green/pink mold: discard whole batch. Always submerge food under brine.
Why does temp matter?+
Microbial activity doubles per ~18°F (Q10 rule). 60°F sauerkraut takes twice as long as 78°F.
Salt percentage?+
Sauerkraut/kimchi: 2-2.5% by weight. Pickles: 3-5% in brine. Below 1.5%: bad bacteria; above 5%: too salty + lacto inhibited.
Refrigerator slows or stops?+
Slows dramatically — 100× slower at 40°F vs. 70°F. Effectively halts active fermentation; stable for months.

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