Fermentation Calculator
Calculate fermentation time based on temperature and recipe type.
Get estimated timelines for bread, beer, wine, and fermented vegetables.
Fermentation time and temperature are the two most critical variables in any fermentation project. Temperature governs microbial activity rate — too cold and fermentation stalls; too hot and you kill your culture or produce off-flavors.
General fermentation rate relationship:
Q10 Rule: Rate doubles for every 10°C (18°F) temperature increase
Estimated Days = Reference Days × Q10^((T_reference − T_actual) / 10)
This means fermentation that takes 7 days at 20°C takes approximately 3.5 days at 30°C — and 14 days at 10°C.
Temperature guidelines by fermentation type:
| Type | Optimal Temp | Fermentation Time |
|---|---|---|
| Bread dough (active yeast) | 75–85°F (24–29°C) | 1–2 hours (first rise) |
| Sourdough bread | 72–78°F (22–26°C) | 4–12 hours |
| Kombucha (SCOBY) | 75–85°F (24–29°C) | 7–14 days |
| Yogurt (Lactobacillus) | 100–115°F (38–46°C) | 4–8 hours |
| Sauerkraut / kimchi | 65–75°F (18–24°C) | 3–7 days |
| Kefir (milk) | 68–77°F (20–25°C) | 24–48 hours |
| Ale beer (S. cerevisiae) | 65–72°F (18–22°C) | 7–14 days |
| Lager beer (S. pastorianus) | 48–55°F (9–13°C) | 4–6 weeks |
| Wine | 50–90°F (10–32°C) | 1–4 weeks |
Salt concentration for vegetable ferments:
Salt % by weight = Salt / (Vegetables + Salt) × 100
Ideal range: 2–3% salt by weight — inhibits harmful bacteria while allowing Lactobacillus to thrive.
Worked example — sauerkraut: 1 kg cabbage | 20 g salt: Salt % = 20 / (1000 + 20) = 1.96% → slightly low; use 25 g for a safer 2.4%.
pH monitoring: Successful vegetable fermentation drops pH from ~6 to below 4.6 within the first 48 hours — below this level, harmful bacteria cannot survive.