Fermentation Temperature Guide: Timing Your Sourdough Perfectly

How Temperature Controls Fermentation

Yeast and lactic acid bacteria grow exponentially as temperature rises — a 10°F increase can cut fermentation time in half. This is the single most underestimated variable in home sourdough baking.

Temperature Ranges (with 20% starter)

65°F: Very slow, 18–24 hours. Deep, complex flavor.
70°F: Slow, 12–16 hours. Great for overnight bulk ferments.
75°F: Moderate, 8–12 hours. The standard reference point.
80°F: Fast, 6–8 hours.
85°F+: Very fast, 4–6 hours. High risk of over-fermentation.

Practical Tips

Buy a cheap digital probe thermometer and actually measure your room temperature — “room temp” is not a fixed number. It varies by 10°F+ between summer and winter, and between floor level and countertop.

Use our calculator to input your room temperature and get a fermentation time estimate tuned to your kitchen.