A yeast bread recipe gives a packet of yeast and a rise "until doubled". Sourdough needs a different amount, a different signal and a different clock. This guide converts a lean yeast recipe step by step: the levain amount, the water to hold back so the dough comes out as wet as the original, and the times the calculator's model predicts at your kitchen temperature.
Which recipes this works for
This method is for lean breads: flour, water, salt and yeast, as in a basic white loaf, a country loaf, a baguette-style dough or a plain sandwich loaf baked in a loaf pan. Doughs with sugar, butter, milk or eggs (brioche, sandwich loaves with milk and butter, cinnamon rolls) are outside the calculator's model. Sugar and fat change how fast the dough ferments, so the times below do not apply to them. For pizza, see sourdough vs. yeast pizza dough instead.
The conversion in three moves
The method uses the convention of the bake schedule calculator: the levain amount is the weight of ripe levain divided by the weight of the flour you add, with the levain at 100% hydration (equal weights of flour and water). How much starter in sourdough explains the convention and the other ways recipes count.
- Keep the recipe's flour and salt. The flour you add stays what the recipe says.
- Replace the yeast with 20% levain. For 500 g of flour that is 100 g of ripe levain. Leave the yeast out entirely: with both, the yeast sets the pace and the times below do not apply.
- Take the levain's water and flour into account. Half the levain's weight is water and half is flour. Reduce the recipe's water so the total hydration, counting the levain, matches the original.
Some guides do it the other way and subtract the levain's flour and water from the recipe. You end up with a similar dough; this guide follows the calculator so the numbers match what it shows.
A worked example: 500 g flour at 70% water
The yeast recipe: 500 g flour, 350 g water (70%), 10 g salt and a packet of instant yeast.
If you simply swap the yeast for 100 g of levain and keep the 350 g of water, the dough has 550 g of flour and 400 g of water in total. Its true hydration is 72.7%, wetter than the recipe. That is plain arithmetic, not a model.
To keep it at 70%, the 550 g of total flour needs 385 g of total water. The levain brings 50 g of that, so you add 335 g of water: hold back 15 g of the recipe's 350 g. In the calculator's Recipe Lab, that is 67% water on the flour you add, and it shows a true total hydration of 70%.
The converted recipe:
- 500 g flour
- 335 g water
- 10 g salt
- 100 g ripe levain (20%)
The dough now has 50 g more flour and 35 g more water than the original (85 g in all), so the loaf comes out about a tenth heavier. For the same loaf size, for example in the same loaf pan, scale every ingredient down by a tenth: 450 g flour, 302 g water, 9 g salt and 90 g levain. Keep the water you held back handy (15 g, or about 14 g in the scaled-down version): if the dough feels stiffer than the original, add some of it during mixing.
Step 1: build the levain to its peak
To get 100 g of ripe levain, mix 25 g of starter with 50 g of flour and 50 g of water (a 1:2:2 feed; that makes 125 g, so use 100 g in the dough, and the 25 g left over can go back into your starter jar or be discarded) and let it rise to its peak. The model predicts that peak at about 5½ h at 22°C (72°F). The starter feeding ratio guide has the times for other ratios and temperatures. Use starter that was fed within the last day, not straight from the fridge. The peak is when it has risen and domed and is just starting to level off; whether that is double depends on the starter. If it barely moves, see sourdough starter not doubling.
Step 2: mix
Mix the flour, the water you add and the levain, then the salt. Water at a temperature that brings the dough to about the kitchen temperature keeps the times below honest; the DDT formula works it out. Put the dough in a straight-sided container and mark the level.
Step 3: bulk to a 50–75% rise, not "until doubled"
Bulk is where the yeast recipe's first rise was, and the cue changes. Instead of waiting for the dough to double, end bulk at about a 50–75% rise, with a domed top, a jiggle when you shake the container and bubbles at the sides. Bulk fermentation by temperature describes those signs. Doubling is a 100% rise, past that window. Sets of stretch and folds in the first hours of bulk build strength in place of long kneading; stretch and fold gives the number of sets.
With 20% levain, the model predicts bulk to a 50–75% rise of about 7½ h at 20°C (68°F), 6 h at 22°C (72°F) and 5 h at 24°C (75°F). That is far longer than the first rise in a yeast recipe.
The levain amount moves the time less than temperature does. The model multiplies the 20% bulk time by (20 ÷ levain %)^0.4: about 1.32 for 10% levain and 0.85 for 30%. At 22°C (72°F) the model predicts about 8 h with 10% and 5¼ h with 30%. The model's levain term is fitted to The Sourdough Journey's bulk fermentation timetables (5–20% levain, 19–23°C) and matches that data best at 10–20%, so outside 10–20%, as with the 30% figure here, its times are an extrapolation.
The model assumes the room holds one temperature and the flour is white bread flour. A kitchen that cools during the day slows the dough, and whole-grain flour ferments faster (whole-wheat sourdough). Go by the dough's signs, not the clock.
Step 4: shape
Pre-shape into a loose round, rest 20–30 minutes, then shape as the recipe says: a round or oval for a banneton, a log for a loaf pan. Sourdough at the end of bulk is softer and airier than a yeast dough after its first rise, so handle it gently and do not knock the air out.
Step 5: final proof or cold retard
The yeast recipe's proof time does not carry over either. For a same-day loaf, the calculator's rule is a final proof of about half the bulk time at the proof temperature, counted as for 20% levain if you use less. At 22°C (72°F) with 20% levain, the model predicts a final proof of about 3 h; start checking after about 2¼ h. With more than about 30% levain the proof can run longer than the model predicts. It is a rule of thumb, not a measurement: the poke test decides, as how long to proof sourdough explains. A floured fingertip pressed about 1 cm in should leave a dent that fills back slowly.
Or shape it and put it in the fridge overnight, then bake it cold in the morning. The model does not cover fridge time; cold retard vs. same-day explains how to plan the retard and how to tell the loaf is ready.
Step 6: bake
About an hour before the start-checking time, start preheating the oven to 250°C (480°F) with the Dutch oven (or the stone and a steam tray) inside, for 60 minutes. Score the loaf and bake it covered or with steam. For a free-form loaf, the site's usual method is 20 minutes covered at 250°C (480°F), then about 25 minutes uncovered at 230°C (445°F); bake a loaf in a loaf pan at the temperature the yeast recipe gives. It is done at 96–99°C (205–210°F) in the center (common practice; see why sourdough is gummy). Cool it at least 1 hour before slicing.
The whole plan at a glance
For the converted recipe with 20% levain, the model predicts:
| Kitchen | Levain peak (1:2:2 feed) | Bulk with 20% levain, to a 50–75% rise | Final proof: start checking | Final proof: typical |
|---|---|---|---|---|
| 20°C (68°F) | about 6½ h | about 7½ h | about 2½ h | about 3¾ h |
| 22°C (72°F) | about 5½ h | about 6 h | about 2¼ h | about 3 h |
| 24°C (75°F) | about 4½ h | about 5 h | about 1¾ h | about 2½ h |
Add about 30 minutes for the pre-shape, bench rest and shaping between bulk and proof. In a 22°C (72°F) kitchen, a levain built at 7 a.m. puts the mix at about 12:30 p.m., shaping done by about 7 p.m., the oven on at about 8:15 p.m., the first poke test at about 9:15 p.m. and the loaf in the oven at about 10 p.m. by the model's times, or the next morning with a cold retard.
Frequently asked questions
How much starter replaces a packet of yeast?
There is no fixed swap, because the starter changes the timing rather than standing in for the yeast gram for gram. With the calculator's convention, 20% of the flour as ripe levain is a common middle ground: 100 g for 500 g of flour. For other amounts and what they do to bulk, see how much starter in sourdough.
Can I convert a brioche or a milk bread this way?
Not with these numbers. Sugar, butter, milk and eggs are outside the calculator's model, so the times above do not apply to enriched doughs.
Can I do the bulk overnight instead?
Mainly in a cool kitchen. On its own, using less starter makes the bulk only a few hours longer. Overnight bulk fermentation gives the starter amount for your night.
Plan your converted recipe
Put your flour, water, starter amount and kitchen temperature into the bake schedule calculator. Its Recipe Lab shows the true hydration with the levain counted, and the schedule gives the bulk and proof times for your kitchen.