Yeast to Sourdough Starter Converter
How to Convert Any Recipe From Commercial Yeast to Sourdough Starter
TL;DR: Replace 1 teaspoon of instant yeast with approximately 113g (about half a cup) of active sourdough starter. Reduce the recipe's flour by half the starter weight and water by the other half. Expect bulk fermentation to take 4–12 hours instead of 1–2. This calculator does all the math automatically.
You've got a jar of beautiful, active sourdough starter and a recipe that calls for a packet of yeast. Those two things don't have to stay separate forever.
Almost any yeast bread — sandwich loaves, dinner rolls, cinnamon rolls, pizza dough, focaccia — can be converted to sourdough starter. The flavor gets better. The texture gets chewier. The bread keeps longer. And you stop buying those little packets.
How the Conversion Works
Commercial yeast is concentrated leavening — one 7g packet (2¼ teaspoons) of instant yeast contains the equivalent leavening power of about 113g of active sourdough starter. The difference is speed: commercial yeast acts in 1–2 hours. Sourdough starter takes 4–12 hours. That extra time is where the flavor comes from.
When you add starter to a recipe, you're also adding flour and water — a 100% hydration starter is exactly 50% flour and 50% water by weight. Add 100g of starter and you've added 50g of flour and 50g of water to your recipe. The calculator subtracts those amounts from your recipe totals so your dough stays the right consistency.
| Commercial Yeast | Starter Equivalent | Bulk Rise |
|---|---|---|
| ¼ tsp instant | ~28g starter | 6–12 hrs |
| 1 tsp instant | ~113g starter | 4–8 hrs |
| 1 packet (2¼ tsp) | ~200g starter | 4–6 hrs |
| 1 tsp active dry | ~90g starter | 5–10 hrs |
The One Rule That Never Changes
Your starter must be active and at peak when you use it. Feed it 4–8 hours before you plan to bake. Wait for it to double. Use it at peak rise — when the top is domed and full of bubbles. Flat, unfed starter sitting in your fridge will not leaven bread regardless of how much you use.
For your first conversion try, our sourdough bread recipe is a good starting point. Our feeding guide will help you time your starter's peak for when you need it.
Don't have a starter yet? The Mother is a 288-year-old live culture that ships free with postage. She converts to any recipe beautifully — we've baked her into sandwich loaves, cinnamon rolls, pizza dough, and focaccia.