How it works: Same model as the sourdough schedule planner: bulk time = (5.5 h + 1.5 h for each halving of starter below 20%) × 2^((24 - T) ÷ 6.75) × flour factor, where T is the dough temperature in °C, with a ±15% range. Flour factors: mostly white 1, up to 30% whole grain 0.9, mostly whole wheat 0.8, mostly rye 0.75, since whole grains feed the culture faster. Target rise: about 75 to 100% below 22 °C, 50 to 75% from 22 to 26 °C and 30 to 50% above 26 °C, because warm dough keeps fermenting quickly after shaping. All figures are rules of thumb.

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How long will my dough take?

Bulk fermentation is the long first rise after mixing, and it is where most of a sourdough loaf’s flavour and structure develop. It is also the stage recipes are vaguest about, because the honest answer depends on how warm your dough is, how much starter went in and what flour you used. This estimator takes those three things and gives you a realistic time window plus a target rise to look for.

It suits home bakers who want to know roughly when to be back in the kitchen.

What changes the timing

Yeast and lactic acid bacteria speed up as they warm and slow down as they cool. A useful rule of thumb is that every 7 °C of cooling roughly doubles the time. Starter percentage matters too: more starter means more active microbes from the first minute, so the dough gets there sooner.

Flour is the third lever. Whole wheat and rye carry more nutrients and enzymes than white flour, which feeds the culture faster, so a dough with a good share of whole grain usually finishes bulk earlier.

The estimator uses the same model as the sourdough schedule planner, so the two tools always agree for a mostly white dough.

Filling it in

Measure the dough straight after mixing and enter it as Dough temperature. The room temperature is not the same thing, especially if you mixed with warm or cold water.
Enter Starter as a percentage of total flour.
Choose the closest option under Flour: Mostly white flour, Up to 30% whole grain, Mostly whole wheat or Mostly rye.

You get Bulk time (guide) as a range, the Target rise (guide), the Middle of the range, and two rows showing how the time moves if the dough runs a little warmer or cooler.

A walkthrough with real numbers

Your country loaf uses 15% starter and about a fifth of the flour is whole wheat. After mixing, the probe reads 23 °C. With Up to 30% whole grain selected, the estimator shows:

Bulk time (guide): about 5 h 15 min to 7 h
Target rise (guide): about 50% to 75%
Middle of the range: 6 h
At 25 °C: about 4 h 15 min to 5 h 45 min
At 21 °C: about 6 h 15 min to 8 h 30 min

The last two rows show why dough temperature is worth controlling. Two degrees either way shifts the whole window by more than an hour.

Switch Flour to Mostly white flour and the same dough stretches to about 5 h 45 min to 7 h 45 min, with the middle at 6 h 45 min. The whole grain version is quicker because there is more for the culture to eat.

Now picture a hot day where the dough comes off the mixer at 26.5 °C. The window drops to about 3 h 30 min to 5 h, and the target rise falls to about 30% to 50%.

Why the target rise changes with temperature

A warm dough keeps fermenting quickly while you pre-shape, shape and proof it, so it needs to stop bulk earlier or it will overproof later. A cool dough slows down after shaping, so it can go further in bulk. The bands here, about 75 to 100% below 22 °C, 50 to 75% from 22 to 26 °C and 30 to 50% above that, are rules of thumb rather than laws. Your flour and starter will nudge them.

Reading the dough

Use a straight-sided container. Mark the starting level with tape, then judge the rise against it rather than guessing.
Look for more than height. A dough near the end of bulk has a slightly domed surface, bubbles along the sides and a wobble when you shake the tub.
Keep the temperature steady. A dough in a cold corner can lose a degree or two and drift well past the estimate.
Hit your target temperature on purpose. The dough water temperature calculator tells you how warm to make the mixing water.

If your starter percentage came from a recipe you are designing, the sourdough recipe builder measures starter against total flour too, so you can copy the figure over unchanged.

Bulk fermentation questions

Why does the estimate give a range instead of one time?

Starters differ in strength, and flours vary from bag to bag. The range covers the usual spread for a healthy starter; your own dough decides where in it you land.

My dough doubled in less time than shown. Is that a problem?

It usually means the starter is very lively or the dough was warmer than you measured. Shape it as soon as it looks ready, and next time use a little less starter or cooler water.

Should I count the folds as part of bulk?

Yes. Bulk runs from the moment the starter goes in until you pre-shape, and stretch and folds happen during that time.

Does salt slow fermentation?

A little, but at the usual 2% of flour the effect is already built into typical timings.

Can I pause bulk in the fridge?

You can, but cold stops the clock unevenly and the estimate no longer applies. Most bakers finish bulk at room temperature and use the fridge for the shaped loaf instead.