Sourdough Bulk Fermentation Calculator
Bulk fermentation, the first rise after mixing, is where sourdough loaves are made or lost. The time in a recipe is only a guide: dough temperature and the amount of starter can change it by hours.
Enter your dough's temperature and starter percentage to get an estimated bulk window, a clock-time plan and the rise to look for, so you know when to stop.
Estimated bulk fermentation
EstimateSigns bulk is done
- The dough has risen by about the target above.
- The surface is domed and slightly jiggly, with bubbles on the top and sides.
- It feels airy and light, and pulls away cleanly from the container.
A rule-of-thumb estimate for a healthy starter at around 100% hydration. Watch the dough, not the clock.
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How to use it
- 1
Right after mixing, measure the temperature of the dough itself with a probe thermometer.
- 2
Enter the starter or levain as a percentage of the recipe's flour (starter ÷ flour × 100).
- 3
Optionally, add the time bulk starts to get a clock-time window.
- 4
Put the dough in a straight-sided container and mark its starting level so you can judge the rise.
- 5
Start checking at the beginning of the window, and end bulk when the dough reaches the target rise and shows the signs listed.
The math, explained
Bakers work with a desired dough temperature (DDT) because temperature drives fermentation speed more than anything else you control. Many sourdough bakers and books aim for about 24–26 °C (75–78 °F).
This calculator uses a clearly labelled rule of thumb: a dough with 20% starter at 24 °C (75 °F) finishes bulk in about 4–6 hours, with 5 hours as the centre estimate.
Starter percentage: less starter means a longer bulk. The estimate multiplies the time by about 1.35 at 10% starter, 1.15 at 15%, 1 at 20% and 0.8 at 30%. That's about 6.75 h at 10% starter and 4 h at 30%.
Temperature: fermentation roughly doubles in speed for every 9 °C (16 °F) warmer and halves for every 9 °C cooler, so hours = 5 × starter factor × 2^((24 − dough °C) ÷ 9). The window shown runs from 80% to 120% of that figure, rounded to the nearest half hour.
Example: 15% starter in dough at 22 °C gives 5 × 1.15 = 5.75 h, multiplied by 2^(2 ÷ 9) ≈ 1.17 for about 6.7 hours, shown as a window of roughly 5.5–8 hours.
Rise targets follow a common baker's rule: the warmer the dough, the earlier you stop, because fermentation keeps going quickly through shaping and proofing.
Frequently asked questions
How long should sourdough bulk fermentation take?
Anywhere from about 3 hours in a warm kitchen to 12 hours or more in a cool one. With around 20% starter and dough at 24–26 °C (75–78 °F), 4–6 hours is typical. Judge by the rise and feel of the dough rather than a fixed time.
How much should sourdough rise during bulk fermentation?
A common target is 50–75% for dough at around 22–26 °C (72–78 °F). Cooler dough can go further, towards 75–100%; warm dough should stop nearer 30–50%, since it keeps fermenting quickly while you shape. A straight-sided container makes the rise easy to measure.
What dough temperature is best for sourdough?
Most bakers aim for 24–26 °C (75–78 °F). It gives a manageable bulk of a few hours and a balanced flavour. Use warmer or cooler water when mixing to steer the dough towards that range.
What happens if I over-ferment sourdough?
Over-fermented dough turns slack, sticky and hard to shape, can smell boozy or very sour, and bakes into a flat loaf with a dense or gummy crumb. If your dough is racing ahead, shape it early or move it to the fridge to slow it down.
Does cold retarding count as bulk fermentation?
Usually not. Bulk is the first rise at room temperature; cold retarding in the fridge normally happens after shaping. Dough keeps fermenting slowly while it cools down, which is another reason to end a warm bulk at the lower rise target.
More sourdough calculators
- Sourdough Hydration Calculator Find your dough's true hydration with the starter's flour and water counted in, plus baker's percentages and a reverse mode for target hydration.
- Sourdough Starter Feeding Calculator Grams of starter, flour and water for any feeding ratio, plus an estimated time to peak at your kitchen temperature.
- Levain Build Calculator Build exactly the levain your recipe needs: starter, flour and water in grams from the levain weight or percentage, with a buffer.
- Baker's Percentage Recipe Scaler Convert any bread recipe to baker's percentages and scale it to more loaves, a target dough weight or a simple multiplier.
Keep reading
- Cold Proof Sourdough: How Long, What Temperature and Why
How long to cold proof sourdough in the fridge, the best fridge temperature, when to start the cold retard, and how to bake straight from the fridge.
- Over-Proofed Sourdough: Signs, Causes and How to Save It
How to tell over-proofed from under-proofed sourdough, what the poke test really shows, why it happens, and how to rescue dough that went too far.