How to Convert Any Recipe to Sourdough (The 1:1:1 Ratio)

You start to make a recipe only to be disappointed when you realize you’re out of buttermilk, milk, or yogurt. Or maybe now that you know how to feed your sourdough starter you’re looking for a simple way to use up the sourdough discard sitting in your fridge. Or perhaps you just want to try a sourdough version of your own family’s recipes.

The secret to all these problems comes down to simple baking chemistry—and a single conversion rule that works in almost any recipe containing flour and liquid.

The Secret Ingredient: Natural Acidity

To understand why sourdough works as a universal quick-swap, it helps to look at how chemical leaveners like baking soda work.

Remember the classic volcano science experiment? When you mix baking soda (a base) and vinegar (an acid), the chemical reaction bubbles violently due to the release of carbon dioxide gas. That is exactly how baking soda works in your oven. Those gas bubbles get trapped in your dough and expand to give your quick breads, muffins, and biscuits their lift.

If a recipe calls for baking soda, it relies on an acidic ingredient—like buttermilk, yogurt, or vinegar—to activate it. If you swap out buttermilk for neutral water or plant milk without replacing the acid, the baking soda never activates fully. You end up with dense baked goods and a bitter, soapy aftertaste from unreacted baking soda.

This is where sourdough starter saves the day. Because sourdough starter is naturally acidic, it provides that acid kick needed to activate baking soda—while also supplying flour and hydration to your batter.

The 1:1:1 Sourdough Conversion Rule

Standard sourdough starter is maintained at 100% hydration—meaning it consists of equal parts flour and water by weight. However, as sourdough starter ferments, natural enzymes break down the flour’s gluten proteins and starches, turning a thick paste into a smooth, pourable liquid.

Because starter breaks down into such a fluid consistency, you can use this simple 1:1:1 volume rule for pretty much any recipe that calls for flour and a liquid:

I’ve used this method for over 3 years on countless recipes and have always had great results!

The Math in Practice:

If your favorite muffin recipe calls for 2 cups of flour and 1 cup of milk, and you want to use 1 cup of sourdough starter:

• The Flour: Subtract 1 cup. You now need 1 cup of flour.
• The Liquid: Subtract 1 cup. You no longer need any milk.
• The Result: Your starter provides the liquid, some flour, and the natural acidity needed to lift the batter.

Pro-Tip: The 48-Hour Starter Window

While you can use “discard” that’s been sitting in the back of the fridge for a week, this method works best if your starter has been fed within the last 48 hours. A relatively fresh starter has a better, less acidic flavor, ensuring your pancakes, biscuits, or cakes rise high without becoming too tangy. I admit at times I have used some pretty starved sourdough for this method and it made my baked goods taste like I had added vinegar or lots of lemon juice to the recipe.

Quick rule of thumb: If your sourdough smells sharp like vinegar, don’t use it until it’s been fed. If it still smells yeasty and pleasant it’s fine to use right away.

Why This Belongs in Your Kitchen Toolkit

• Zero Waste: It provides an easy, consistent outlet for your weekly sourdough discard.
• Pantry Stand-In: If you run out of buttermilk or milk, starter steps in as both liquid and acid.
• Versatility: Works in everything from pancakes and waffle batters to pizza dough, cookies, and brownies.
• Vegan: You can make fantastic vegan baked goods for friends and potlucks without buying specialty ingredients.

“As he that taketh away a garment in cold weather, and as vinegar upon nitre, so is he that singeth songs to an heavy heart.”

Proverbs 25:20

Note: “nitre” = baking soda