How to Convert a Yeast Recipe to Sourdough
To convert a yeast bread to sourdough, leave out the yeast, add active starter equal to about 20% of the recipe’s flour weight, and take the starter’s own flour and water out of the recipe. Then plan for rises that take two to three times as long.
- 5 min read
- Updated 2026-11-03
Printable chart
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| Starter hydration | Flour in the starter | Water in the starter | Flour to add | Water to add |
|---|---|---|---|---|
| 50% (stiff) | 66.7 g | 33.3 g | 433.3 g | 316.7 g |
| 75% | 57.1 g | 42.9 g | 442.9 g | 307.1 g |
| 100% (equal weights) | 50 g | 50 g | 450 g | 300 g |
| 125% (loose) | 44.4 g | 55.6 g | 455.6 g | 294.4 g |
Hydration is the starter’s water as a percentage of its flour. Total flour and water stay at 500 g and 350 g, so the dough keeps its 70% hydration.
Scale your ingredients
If you want a bigger or smaller loaf, scale the original yeast recipe in the scaler below first (it starts at 1), then convert the scaled amounts with the steps that follow. Weigh the flour and water if you can; the conversion is much easier in grams.
Step 1: Get the recipe’s flour and water in grams
Add up all the flour, including any whole wheat or rye, and all the water. If the recipe uses cups, convert flour at about 120 grams per spooned cup, so 4 cups becomes about 480 grams; cups of flour in grams has the details. If the liquid is milk, count its full weight as liquid for this rough conversion; it is mostly water, though the dough may feel a little stiffer. Write down both totals, because they stay fixed through the conversion.
Step 2: Choose how much starter
Use active, bubbly starter at about 20% of the total flour weight: 100 grams for 500 grams of flour. Our yeast converter’s rule of thumb is 100 to 200 grams of starter per 7-gram packet of yeast, which for a 500-gram loaf is 20 to 40% of the flour; 20% sits at the low end and gives a steady rise. Less starter, such as 10%, rises more slowly and suits an overnight ferment; more, up to about 40%, speeds things up. Feed the starter ahead so it is near its peak when you mix; the sourdough starter calculator works out the feeding.
Step 3: Subtract the starter’s flour and water
Starter is flour and water, so both count toward the recipe’s totals. Divide the starter’s weight by 1 plus its hydration written as a decimal (100% is 1, 50% is 0.5) to find its flour: 100 grams of 100% starter holds 50 grams of flour and 50 of water. Take those amounts out of the recipe, then add the starter. The chart shows the same split for stiffer and looser starters. Keep the salt as written, since it is based on total flour, and leave out the commercial yeast. The sourdough hydration calculator double-checks the result.
Step 4: Plan for a longer rise
Sourdough works more slowly than packaged yeast, so expect the first rise to take roughly two to three times as long as the original recipe says, and longer in a cool kitchen. Judge the dough rather than the clock: it should look puffy, feel airy and show bubbles on the sides and surface. Shape as the original recipe directs, then let it rise until a gentle press springs back slowly. A night in the refrigerator for the shaped loaf suits sourdough well, adds flavor and lets you bake in the morning.
Recipes that convert well, and ones that need care
Lean breads made from flour, water, salt and a little oil or sugar convert most easily. Rich doughs with plenty of sugar, butter, eggs or milk rise far more slowly on starter alone, and a long sourdough rise runs into food-safety limits. For doughs with eggs or milk, do the long, slow stages in the refrigerator rather than on the counter, and refrigerate any unused raw egg right away; the FDA’s storage guidance says not to leave eggs and other foods that need refrigeration at room temperature for more than 2 hours (1 hour above 90°F). Don’t taste raw dough or starter, either: the FDA advises against eating raw dough, because baking is what kills bacteria in flour.
Frequently asked questions
How much sourdough starter replaces one packet of yeast?
About 100 to 200 grams of active starter per 7-gram packet. For a loaf with 500 grams of flour that is 20 to 40% of the flour; 20% is a good place to start.
Do I need to change the flour and water when I add starter?
Yes. Subtract the starter’s flour and water from the recipe. With a 100% hydration starter, that is half its weight from each.
How long does a converted sourdough take to rise?
Expect roughly two to three times the original rise time, and more in a cool kitchen.
Can I keep a little yeast along with the starter?
Yes. A small amount of yeast gives a faster, more predictable rise; the result is a hybrid dough with a milder sour flavor.