Hi Kate, there isn't an exact equivalent formula for converting a yeast-raised recipe to sourdough. Keep in mind that the resulting flavor and texture will be different when converting a recipe to sourdough, and rise times will likely be at least twice as long as the rise times indicated with yeast. That being said, you could certainly try substituting about 227g ripe starter for a recipe calling for 2 1/4 teaspoons (1 packet) of dry yeast. In order to do so, you'll need to remove 114g of liquid and 113g of flour from the original recipe. The sourdough recipes that we offer on the website that include both yeast and sourdough will be a great place to start, since you can easily remove the yeast from those recipes and extend the rise times when using ripe, active starter (with no other adjustments necessary). We also have several entirely naturally leavened sourdough bread recipes for you to choose from. Here are a few of my favorites:  No-Knead Sourdough Bread, Pain Au Levain, Pain de Campagne, Vermont Sourdough, Naturally Leavened Sourdough, Artisan Sourdough Bread Made With Stiff Starter, and Extra-Tangy Sourdough. That should be enough to get you going! Happy sourdough baking!

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