Bulk fermentation calculator
Bulk fermentation time depends mostly on two numbers: how warm the dough is and how much starter it has. Enter both and LoafMath estimates how long bulk takes, when it ends and how much the dough should rise.
- Measure the dough, not the room. Dough often runs a few degrees cooler.
- The time is an estimate. Bulk is done when the dough reaches its target rise.
Sourdough bulk fermentation chart
Estimated bulk time by dough temperature and starter amount, with the rise to aim for at each temperature. The cell closest to your dough is highlighted. Print it and keep it next to your bowl.
| Dough temp | 5% starter | 10% starter | 15% starter | 20% starter | 25% starter | 30% starter | Aim for rise |
|---|---|---|---|---|---|---|---|
| 18 °C 64 °F | 13 h | 11 h | 9½ h | 8½ h | 7½ h | 7 h | 75% |
| 20 °C 68 °F | 11 h | 9 h | 8 h | 7 h | 6½ h | 6 h | 75% |
| 22 °C 72 °F | 9½ h | 7½ h | 6½ h | 6 h | 5½ h | 5 h | 70% |
| 24 °C 75 °F | 8 h | 6½ h | 5½ h | 5 h | 4½ h | 4 h | 55% |
| 26 °C 79 °F | 6½ h | 5½ h | 4½ h | 4 h | 4 h | 3½ h | 40% |
| 28 °C 82 °F | 5½ h | 4½ h | 4 h | 3½ h | 3 h | 3 h | 30% |
| 30 °C 86 °F | 4½ h | 4 h | 3½ h | 3 h | 2½ h | 2½ h | 30% |
How long should sourdough bulk ferment?
With 20% starter, bulk takes about 5 hours for a dough at 24 °C (75 °F). The same dough needs about 7 hours at 20 °C and about 3½ hours at 28 °C. Those are starting points. Your starter and flour move them, so watch the dough as it gets close.
Temperature changes bulk time the most
The yeast and bacteria in a starter work faster in warm dough. In this estimate, bulk time roughly halves for every 8 °C (14 °F) warmer. That is why the same recipe can finish in the early afternoon in summer and in the evening in winter.
Starter amount changes it too
Less starter means fewer microbes at the start, so the dough needs more time to build up. At 24 °C, bulk takes about 5 hours with 20% starter, about 6½ hours with 10% and about 8 hours with 5%. Halving the starter does not double the time, because the microbes multiply. Cutting the starter is a simple way to slow a warm kitchen down.
How do you know bulk fermentation is done?
Go by the rise. Warm dough should stop at a smaller rise than cool dough, because it keeps fermenting quickly while you shape and proof it. Aim for about 75% at 21 °C, 55% at 24 °C and 30% at 27 °C. A straight-sided container with the starting level marked makes the rise easy to read. At the end of bulk the top is domed, there are bubbles at the edges, and the dough wobbles when you shake the container.
Bulk fermentation FAQ
How long is bulk fermentation for sourdough?
With 20% starter, LoafMath estimates about 5 hours at 24 °C (75 °F), about 7 hours at 20 °C (68 °F) and about 3½ hours at 28 °C (82 °F). Less starter takes longer: about 6½ hours with 10% at 24 °C. End bulk by the rise, not the clock.
What is the best temperature for bulk fermentation?
Most sourdough recipes aim for a dough at 24–26 °C (75–78 °F). Cooler dough works too and gives you more time between checks, but bulk runs longer. Use the dough temperature calculator to pick the water temperature that gets you there.
How much should sourdough rise during bulk fermentation?
It depends on the dough temperature. Warm dough needs a smaller rise because it keeps fermenting fast after shaping. As a guide, aim for about 75% at 21 °C (70 °F), 55% at 24 °C (75 °F) and 30% at 27 °C (81 °F). This follows The Sourdough Journey’s two-factor method of reading temperature and rise together.
How do I measure the rise?
Put the dough in a straight-sided container and mark its level after mixing. The rise is how far it has climbed compared with that start: dough that started at 4 cm and now sits at 6 cm has risen 50%. Bowls with sloped sides make the dough look higher than it is.
Can I bulk ferment sourdough in the fridge?
Fermentation slows right down in the fridge, so this calculator does not cover it. It is built for dough between 16 and 32 °C (61–90 °F). Many bakers bulk at room temperature, shape, then rest the shaped loaf in the fridge overnight. The bake-day timeline plans that for you.
Why is my bulk fermentation taking longer than the chart?
Check the dough temperature again first: dough often sits a few degrees below the room. A starter used before or long after its peak is slower, and so is a young starter. If the dough is rising, give it time and go by the rise.