Bulk Fermentation Time Calculator
Estimate a sourdough bulk fermentation window from dough temperature, starter percentage and starter activity. Use the result as a prompt to read the dough, not as a fixed finish time.
Estimated window
—
Estimated window
—
Use the clock as a prompt to look at the dough, not as a finish line.
Across temperatures
| Temperature | Window |
|---|
· Free
Track it in Sourdough Tracker.
Plan sourdough bakes with hydration and starter feeding tools in one place.
How to use a bulk fermentation time calculator
A bulk fermentation time calculator can estimate a starting window from dough temperature and starter percentage. This model anchors at 25 C (77 F), 20% recently fed and active starter, and about 4.5 hours for roughly a 50% rise. The estimate is shown as a window because a single time would suggest false precision.
The clock is the weakest signal in sourdough. Look for about 30–50% rise for most recipes—not double—a domed and jiggly surface, bubbles at the edges and a smooth, airy feel. An aliquot jar with a marked, straight-sided sample measures rise more reliably than the bulk container.
Starter strength, flour protein and whole-grain content, hydration and how much the dough is handled can all move the time; none is included in this model. For more planning, see the [sourdough hydration calculator](/tools/sourdough-hydration-calculator) and [starter feeding ratio calculator](/tools/starter-feeding-ratio-calculator).
estimated time = 4.5 × 2^((25 − dough temperature C) ÷ 10) × (20 ÷ starter percentage) The model is limited to about 15–32 C (59–90 F). Outside that range, yeast and bacteria activity diverge and the estimate is shown as a warning rather than a time. The 4–5 hour anchor span is carried into the displayed window.
Bulk fermentation calculator FAQ
Should I stop bulk fermentation when the timer ends?
No. Use the window as a prompt to inspect the dough. A 30–50% rise, domed and jiggly surface, edge bubbles and a smooth, airy feel are more useful signals.
Why does dough temperature change the estimate?
The model uses the supplied Q10 rule: fermentation rate roughly doubles for every 10 C increase over temperatures bakers actually work at.
What if my starter is not recently fed and active?
The calculator adds a warning because the reference point assumes recently fed, active starter. An inactive starter can take longer or may not ferment reliably.
Why is my actual bulk time different?
Starter strength, flour protein and whole-grain content, hydration and handling all affect fermentation, and they are not included in this model.
What is the aliquot jar method?
Place a small sample of the same dough in a straight-sided jar, mark its starting level and watch its rise. It measures change more reliably than judging the bulk container.