The short answer
At a dough temperature of 75°F (24°C), a white flour dough with 20% starter and 75% hydration needs about 3 hours 15 minutes to rise 75%. At 68°F (20°C) the same dough needs about 4 hours 15 minutes. At 82°F (28°C) it needs about 2 hours 30 minutes.
Those numbers are planning estimates. Your starter, flour and kitchen will move them. The chart below shows how the time changes with temperature, starter percentage and flour, and the sections after it explain each factor so you can adjust.
If you want a number for your own recipe, the bulk fermentation chart takes your dough temperature, starter percentage, hydration and flour and returns an estimate.
Bulk fermentation time by temperature
Every time in this table is the time to a 75% rise in volume, with 75% hydration and 2% salt. The starter columns assume a healthy starter that doubles within 4 to 6 hours of a feed. The wholegrain and rye columns use 20% starter and replace all the flour with that kind of flour.
Temperature means the dough temperature after mixing, not the room. Push a probe thermometer into the dough and read it.
| Dough °F | Dough °C | 10% starter | 20% starter | 30% starter | 20% wholegrain | 20% rye |
|---|---|---|---|---|---|---|
| 64°F | 18°C | 9 h 55 min | 5 h | 3 h 20 min | 4 h 30 min | 4 h 15 min |
| 68°F | 20°C | 8 h 30 min | 4 h 15 min | 2 h 50 min | 3 h 50 min | 3 h 35 min |
| 72°F | 22°C | 7 h 20 min | 3 h 40 min | 2 h 25 min | 3 h 15 min | 3 h 5 min |
| 75°F | 24°C | 6 h 30 min | 3 h 15 min | 2 h 10 min | 2 h 55 min | 2 h 45 min |
| 78°F | 26°C | 5 h 50 min | 2 h 55 min | 1 h 55 min | 2 h 35 min | 2 h 30 min |
| 82°F | 28°C | 5 h | 2 h 30 min | 1 h 40 min | 2 h 15 min | 2 h 5 min |
Starter percentage is the weight of starter as a percentage of the total flour in the recipe. If you use 100 g of starter in a recipe with 500 g of flour, that is 20%. Use the sourdough calculator if you want it worked out for a loaf size.
Why temperature changes the time so much
The yeast and bacteria in a starter work faster as the dough warms. The planning model behind this chart, and behind the Zymo app's dough gauge, assumes fermentation runs twice as fast for every 18°F (10°C) of extra warmth. It is a simplification, but it matches what bakers see.
This is why a few degrees matter. Going from 72°F to 78°F is a 6 degree change that cuts bulk by roughly a fifth. A dough that took four hours in winter can finish in under three in a warm kitchen, and a recipe that says "bulk 4 to 6 hours" has no way to know which kitchen you have.
Temperature also changes flavour. Cooler dough ferments more slowly and tends to taste tangier, because the acid-producing bacteria keep working while the yeast lags. Warm dough rises faster and tastes milder. Neither is wrong, so choose the time and flavour you want.
Why starter percentage changes the time
More starter means more yeast and bacteria at the start, so the dough reaches the same rise sooner. In the model, halving the starter doubles the time. Real dough is less exact than that, because a very small amount of starter has to multiply for longer before it makes a difference. Treat the 10% column as a guide, not a promise.
Many home recipes use 15 to 25% starter. Going to 10% lets you run a long, cool bulk overnight. Going to 30% suits a short day when you want bread by evening.
Starter strength matters as much as the percentage. A starter fed 4 hours ago and at its peak is far more active than one that peaked yesterday and sank. If your bakes always run slower than the chart, your starter is probably the reason. Feed it on a regular schedule and use it near its peak. The starter feeding calculator gives exact grams for any ratio.
How flour changes the time
Wholegrain and rye flours ferment faster than white flour. They carry more of the nutrients and enzymes that yeast and bacteria feed on. In the model, wholegrain shortens the time by 10% and rye by 15%. That is why the last two columns are a little shorter than the 20% white column.
Wholegrain dough also absorbs more water, so it may feel stiffer at the same hydration. Rye behaves differently from wheat because it has little gluten, so it does not trap gas the same way. Judge a rye-heavy dough by the clock, the look and the smell, not by a strict volume rise.
A mixed flour dough falls between the columns. For a loaf that is 20% wholegrain and 80% white, expect a time very close to the white column.
How to use the chart
Take your dough temperature right after mixing. Find the nearest row. Pick the column that matches your starter percentage and flour. The time in the cell is when you should start checking, not when you should stop.
Check the dough, not the clock alone. A dough is usually ready when it has grown by about 50 to 75%, the surface looks domed and slightly bubbly, and the edges pull away from the container with a jiggle when you shake it. Mark the starting level with a rubber band or a piece of tape on a straight-sided container, which makes the rise easy to read.
A 50% rise suits a loaf you will shape and proof in the fridge overnight, since it keeps fermenting there. A 75 to 100% rise suits a dough you will bake the same day. The bulk fermentation chart tool shows times for 50%, 75% and 100% rises.
Controlling dough temperature
If the chart says your bulk will run too long or too short for your plans, change the dough temperature or the starter percentage instead of the plan.
To warm a cold dough, mix with warmer water, put the container in an oven with only the light on, or place it in a cooler with a jar of warm water. To cool a hot dough, mix with cold water and keep it out of direct sun. A kitchen thermometer in the dough shows whether the change worked.
Once you know your kitchen, work backward from when you want bread. The sourdough schedule planner turns a target bake time into a timed list of steps, including bulk.
Where this chart can be wrong
The numbers come from a planning model with fixed assumptions, not lab measurements. Hydration, salt, the age of the starter, the type of flour and the size of the dough mass all change real timing. A large batch holds its own heat and often runs faster than a small one.
Use the chart to decide when to start watching, then trust the dough. After two or three bakes, note the actual times next to your dough temperature and starter percentage. Those records fit your kitchen better than any general table.
Frequently asked questions
How long should sourdough bulk ferment at room temperature?
At a dough temperature of 75°F (24°C) with 20% starter, expect about 3 hours 15 minutes to a 75% rise. A cooler room of 68°F (20°C) takes about 4 hours 15 minutes. Check the dough for its rise and shape rather than relying only on time.
What is the best temperature for sourdough bulk fermentation?
Many bakers aim for a dough temperature of 75 to 78°F (24 to 26°C), which gives a bulk of a few hours and a balanced flavour. Cooler dough takes longer and tastes tangier. Warmer dough is faster but has a shorter window before it overproofs.
How do I measure dough temperature?
Push a probe or instant-read thermometer into the center of the dough right after mixing. Room temperature is a poor guide because mixing, flour temperature and water temperature all change the dough.
How much does 10°F change bulk fermentation time?
In the planning model used here, fermentation runs twice as fast for every 18°F (10°C) of extra warmth. So 10°F warmer cuts the time by roughly a third, and 10°F cooler adds roughly half again.
Does more starter make bulk fermentation faster?
Yes. A higher starter percentage shortens bulk. Going from 10% to 20% roughly halves the time in the model, though real dough with very little starter is slower to get going than the math suggests.
How do I know bulk fermentation is done?
Look for a dough that has grown by about 50 to 75%, has a domed, bubbly surface and jiggles when you shake the container. A poke should spring back slowly. Mark the starting level on the container so you can see the rise.
Can I bulk ferment in the fridge?
You can, but it takes much longer. Cold dough ferments slowly, so most bakers do a short warm bulk and then shape and proof in the fridge overnight. For a full cold bulk, use a small amount of starter and plan on many hours. See the bulk fermentation chart for estimates at warmer temperatures.