Convert Yeast Recipe to Sourdough: Starter, Flour and Timing

Updated September 2026 · Baking Resources

Convert yeast recipe to sourdough in one line: take the yeast out, add active starter equal to 20 percent of the recipe's total flour weight, then subtract the flour and water inside that starter from the dough so the totals stay exactly where the recipe put them. At 100 percent hydration a starter is half flour and half water, so 100 g of starter means 50 g less flour and 50 g less water in the dough. Salt, sugar, butter and eggs stay as written.

The ingredient list barely changes. The schedule does. Expect fermentation to take roughly twice as long as the yeasted version, and judge it by the dough rather than the clock.

Going the other way works too. A sourdough formula converts back to instant yeast for a same day loaf by adding the starter's flour and water back into the dough and using a small, measured amount of yeast.

Need a yeast amount for a particular rise? Our free yeast converter gives instant, active dry and fresh yeast for any flour weight and rise length, which is the number you need for the reverse conversion and the hybrid method below. Swapping milk, eggs or butter in the same recipe? The baking substitutions finder covers those.

Updated September 2026

What changes and what stays the same

The reason for the subtraction is that a starter is made of flour and water, and the recipe already has the amounts of flour and water it wants. Add 100 g of starter on top of a 500 g flour recipe without adjusting anything and you have made the dough about 10 percent bigger than the pan or the portioning expects. If your starter is stiff, you have also changed the hydration, because a stiff starter brings much more flour than water. Subtracting keeps the recipe the recipe.

Convert yeast recipe to sourdough in five steps

Step 1. Put the recipe in grams. Cups of flour vary by 20 g or more per cup depending on how they are measured, as our how to measure flour guide shows, and the subtraction in step 4 only works with weights. Use 125 g per cup of all-purpose flour, 127 g for bread flour, 236 g per cup of water and 240 g per cup of milk, the figures our converters use.

Step 2. Add up the total flour. If the recipe uses more than one flour, add them together. That number is your 100 percent, the same convention described in our bakers percentage guide.

Step 3. Choose the starter amount. Start at 20 percent of the total flour. For 500 g of flour that is 100 g of active starter, used at or near its peak. The next section covers when to go higher or lower.

Step 4. Split the starter into flour and water, then subtract. Divide the starter weight by 1 plus its hydration to get the flour. The rest is water. At 100 percent hydration that simply means half and half. Take those amounts out of the dough's flour and water.

Step 5. Remove the yeast and keep everything else. Salt stays the same because the starter contains none. Sugar, fat, eggs and flavorings stay the same.

Then check your work. The dough's flour plus the starter's flour should equal the original flour, and the dough's water plus the starter's water should equal the original water. If both match, the conversion is right.

How much starter to use

Twenty percent of the total flour is a reliable default for a lean loaf, but it is a dial rather than a rule.

More starter ferments faster and tastes milder. Less starter ferments slower and tastes more sour, because the bacteria get more hours to build acid. Two things move the choice more than taste does.

Enriched doughs want more starter. Sugar, butter and eggs all slow fermentation, so a brioche or cinnamon roll dough converted at 10 percent may barely move. Start enriched doughs at 25 percent, or use the hybrid method with a pinch of yeast.

A young or sluggish starter wants help. If your starter does not reliably double after a feed, a conversion will be slow at any percentage. Give it several days of regular feeding before an important bake, or use the hybrid method.

A note on how the percentage is counted. This page measures the starter against the recipe's total flour, including the flour inside the starter, because that keeps the original totals fixed. Some sourdough formulas, including the timing chart in our sourdough rise time guide, measure the starter against the dough flour alone. The difference is small. 100 g of starter carved out of a 500 g flour total is 22 percent of the remaining 450 g of dough flour, so that chart's 20 percent row is a fair guide for a dough converted here at 20 percent.

The starter math at any hydration

Most starters are kept at 100 percent hydration, meaning equal weights of flour and water. Stiff starters run drier, and some bakers keep theirs wetter. The formula works for all of them:

Flour in the starter = starter weight divided by (1 + hydration as a decimal)

Water in the starter = starter weight minus the flour

This is where conversions most often go wrong. A baker who keeps a 50 percent starter but subtracts half and half anyway ends up with about 17 g too much flour and 17 g too little water in the dough for every 100 g of starter. That is enough to turn a soft, extensible dough stiff and tight. If you keep a stiff starter, our stiff starter ratio guide covers how to feed and maintain one. For the conversion itself, all you need is its hydration and the formula above.

Why measuring starter by the cup does not work. An active starter at its peak is full of gas, and a cup of it can weigh far less than a cup of the same starter an hour later when it has deflated. A volume measure gives you a different amount of flour and water every time. Weigh the starter, always, and do the subtraction from that weight.

Worked example: a lean loaf in grams

The yeasted recipe:

• Bread flour: 500 g
• Water: 350 g (70 percent)
• Salt: 10 g (2 percent)
• Instant yeast: 7 g (1.4 percent)

Step 1. Choose the starter. 20 percent of 500 g is 100 g of active starter at 100 percent hydration.

Step 2. Split it. 100 divided by 2 is 50 g of flour and 50 g of water.

Step 3. Subtract. Flour: 500 minus 50 = 450 g. Water: 350 minus 50 = 300 g.

Step 4. Remove the yeast and keep the salt.

The 7 g gap in dough weight is simply the yeast that left. Nothing else about the dough changed, so the shaping, the pan and the bake stay the same.

Step 5. Change the method. Mix the flour and water, add the starter and salt, and let bulk fermentation run until the dough has grown by about half to three quarters and feels airy, rather than until a timer goes off. A 1.4 percent yeast dough that was ready in about an hour and a half will take several hours as a sourdough.

Worked example: a recipe written in cups

The yeasted recipe:

• 3 cups all-purpose flour
• 1 cup warm water
• 1 1/2 teaspoons table salt
• 2 1/4 teaspoons active dry yeast (one packet)
• 1 tablespoon olive oil

Step 1. Convert to grams. Flour: 3 x 125 = 375 g. Water: 236 g. Salt: 1.5 x 6 = 9 g. Yeast: 7 g. Olive oil: 216 g per cup divided by 16 is 13.5 g, so call it 14 g.

Step 2. Choose the starter. 20 percent of 375 g is 75 g. Round it to 76 g, which splits evenly into 38 g of flour and 38 g of water.

Step 3. Subtract. Flour: 375 minus 38 = 337 g. Water: 236 minus 38 = 198 g.

Step 4. Check. Flour: 337 + 38 = 375 g. Water: 198 + 38 = 236 g. Hydration: 236 divided by 375 is 63 percent, the same as the original.

Step 5. Keep the rest. Salt 9 g, olive oil 14 g, no yeast.

If you want to keep using measuring cups, 337 g of all-purpose flour is 2 2/3 cups spooned and leveled plus about 4 g, roughly a heaping teaspoon. The 198 g of water is 3/4 cup plus 1 1/2 tablespoons. Weighing is still easier, and it is the only way to measure the starter.

Enriched doughs: milk, butter and eggs

The same subtraction works for sandwich loaves, dinner rolls, cinnamon rolls and brioche. Two things are different: where the starter's water comes from, and where the long hours of fermentation happen.

Take the starter's water from the plain water first, then from the milk. Many enriched recipes use both. Subtract from the water until it runs out, then take any remainder from the milk. Milk is mostly water, so it is close enough for this purpose. Eggs also contain water, but they were already part of the original balance, so leave them alone.

Do any long ferment in the refrigerator, not on the counter. Dough made with milk, butter or eggs should not sit out for an overnight or all day ferment. Keep the room temperature stretch to the active bulk rise, while you can watch it, and use 25 percent starter or the hybrid method so that stretch stays reasonably short. Then shape the dough and move it to the refrigerator for any long rest, such as shaped rolls waiting overnight for a morning bake.

Worked example: an enriched roll dough

The yeasted recipe, converted to grams:

The starter is 120 g, or 24 percent of the flour, which splits into 60 g of flour and 60 g of water. Flour: 500 minus 60 = 440 g. Water: the recipe had 59 g, so the starter's 60 g of water replaces all of it, and the 1 g difference is too small to matter. The milk stays at 240 g.

The method: mix, let the dough ferment in a warm spot until it has grown by about half, shape the rolls, cover them and refrigerate overnight. In the morning, let them finish rising, then bake. With sugar at 10 percent of the flour weight and butter in the dough, this is a slow ferment, which makes it a good candidate for the pinch of yeast described below.

Converting sourdough back to instant yeast

Reverse the subtraction: add the starter's flour and water back into the dough, then add commercial yeast.

1. Split the starter into flour and water using its hydration.
2. Add both back to the dough's flour and water.
3. Remove the starter from the ingredient list.
4. Choose the yeast amount by how long you want to wait. For a standard 2 to 3 hour first rise, our yeast converter works at about 0.7 percent instant yeast by flour weight, which is 3.5 g for 500 g of flour. For an overnight rise in the refrigerator, it drops to about 0.16 percent, or 0.8 g. If your jar holds active dry rather than instant, the yeast converter gives the equivalent, and our guide to active dry vs instant yeast explains why the two differ.

Worked example. The sourdough formula:

• Bread flour: 450 g
• Water: 325 g
• Active starter, 100 percent hydration: 100 g
• Salt: 10 g

The starter holds 50 g of flour and 50 g of water. Add them back: flour 450 + 50 = 500 g, water 325 + 50 = 375 g. Hydration stays at 75 percent. Salt stays at 10 g. For a same day loaf, add 3.5 g of instant yeast, about 1 1/8 teaspoons.

What you give up is flavor. A same day yeasted loaf tastes clean and wheaty rather than tangy. Two ways to bring some of it back:

• Use the overnight yeast amount instead. About 0.8 g of instant yeast and a night in the refrigerator gives a loaf with far more depth than a 3 hour dough.
• Add unfed starter for flavor. Stir in 50 g of starter straight from the refrigerator along with the yeast, and subtract its 25 g of flour and 25 g of water from the dough, exactly as in the forward conversion. It adds a little sour flavor and very little lift.

The hybrid method: starter plus a pinch of yeast

A hybrid dough uses a normal amount of starter for flavor and a very small amount of commercial yeast for reliability. It is the most forgiving way to convert a yeast recipe, and many bakeries use it routinely.

The ratio. Use starter at 15 to 20 percent of the total flour, with the subtraction done as usual, plus 0.1 to 0.2 percent instant yeast by flour weight. For 500 g of flour, that is 0.5 g to 1 g of instant yeast. A level 1/4 teaspoon of instant yeast weighs about 0.8 g, so 1/4 teaspoon is a practical pinch for a 500 g flour dough.

When to use it:

• Enriched doughs. Sugar, butter and eggs slow a starter down. A pinch of yeast shortens the room temperature part of the process, which also helps with the refrigerator rule above.
• A young or unpredictable starter. The yeast guarantees the rise, and the starter still contributes flavor.
• A cool kitchen. A pure sourdough can crawl in a 65°F kitchen. The pinch of yeast keeps it moving.
• A fixed schedule. Hybrid doughs run on a more predictable clock than pure sourdough.

What you give up. A hybrid dough ferments faster, so the bacteria in the starter have less time to build acid, and the loaf is milder than a pure sourdough. For most sandwich breads and rolls, that is an improvement rather than a loss.

Weigh the yeast if you can. A kitchen scale that reads to 0.1 g makes this easy. Without one, a level measuring spoon is far more accurate than a pinch between your fingers.

Timing: what to expect after the conversion

Converting the ingredients takes five minutes. Converting the schedule is the part most people miss.

Bulk fermentation takes about twice as long. A dough that rose in 1 to 2 hours with a packet of yeast will usually need several hours as a 20 percent sourdough. Temperature is the biggest variable, and the full chart by dough temperature and starter percentage is in our sourdough rise time guide.

Judge by the dough, not the recipe's clock. The yeasted recipe probably said "until doubled." For sourdough, end bulk when the dough has grown by about half to three quarters, feels airy and jiggles as one mass. Pushing a sourdough all the way to double often overproofs it.

The final proof is flexible. A shaped lean loaf can finish at room temperature, or rest in the refrigerator overnight and bake in the morning. Enriched doughs should use the refrigerator for any long rest.

Plan backward from the bake. A yeasted recipe fits into an afternoon. A sourdough conversion usually fits better across two days: mix with starter at its peak, bulk ferment while you are home, shape, refrigerate overnight and bake the next morning.

The bake itself does not change. Oven temperature, pan and doneness cues stay as the yeasted recipe gives them.

Troubleshooting a conversion

Frequently asked questions

How much sourdough starter replaces a packet of yeast?

There is no fixed swap, because starter replaces yeast by flour weight rather than packet for packet. Use active starter at about 20 percent of the recipe's total flour, so 100 g for a 500 g flour recipe, and subtract the starter's flour and water from the dough. Remove the yeast completely.

Do I need to change the water when I add sourdough starter?

Yes. A 100 percent hydration starter is half water, so subtract that water from the recipe's water and subtract its flour from the recipe's flour. For 100 g of starter, use 50 g less of each. That keeps the dough's hydration and size exactly where the original recipe had them.

Can I use sourdough discard instead of active starter?

Not as the only leavener. Discard straight from the refrigerator has too little active yeast to raise a loaf in a reasonable time. Use it for flavor alongside commercial yeast, subtracting its flour and water from the dough, or feed it and use it at its peak for a true sourdough conversion.

How do I convert a sourdough recipe to instant yeast?

Add the starter's flour and water back into the dough, remove the starter, and add instant yeast. For a same day loaf with a 2 to 3 hour rise, about 0.7 percent of the flour weight works, which is 3.5 g for 500 g of flour. Keep the salt the same.

Does converting to sourdough change the salt?

No. Starter contains only flour and water, so the recipe's salt stays exactly as written. Because the total flour is unchanged after the subtraction, the salt percentage is unchanged too. Adding extra salt because the ingredient list looks longer is a common mistake that makes the loaf taste harsh.

Can I convert an enriched dough like brioche to sourdough?

Yes, with two adjustments. Use more starter, around 25 percent of the flour, or add a pinch of instant yeast, because sugar, butter and eggs slow fermentation. And do any long or overnight ferment in the refrigerator rather than on the counter, since the dough contains milk, butter or eggs.

How long does a converted sourdough take to rise?

Roughly twice as long as the yeasted version at the same temperature. A 20 percent starter dough usually needs several hours of bulk fermentation. Judge it by a 50 to 75 percent rise and an airy, jiggly dough rather than the clock, and use our rise time guide for the chart by temperature.

What is a hybrid sourdough?

A dough leavened with both starter and a small amount of commercial yeast. A typical ratio is 15 to 20 percent starter plus 0.1 to 0.2 percent instant yeast by flour weight, or about 1/4 teaspoon of instant yeast for 500 g of flour. It rises more predictably and tastes milder than a pure sourdough.

Related guides

• Sourdough Rise Time for bulk and proof times by temperature
• Bakers Percentage for the flour-based math behind every conversion
• Stiff Starter Ratio for feeding and keeping a low hydration starter
• Active Dry vs Instant Yeast for choosing and swapping dry yeasts
• Yeast Converter for yeast amounts by flour weight and rise length
• Substitutions Finder for other ingredient swaps in the same recipe