Sourdough Discard Calculator
This calculator adjusts a recipe's flour and liquid amounts when adding sourdough discard, since discard contains both.
It accounts for discard's roughly 100% hydration (equal parts flour and water).
Because most starters are maintained near 100% hydration, the calculator assumes an even flour-water split in discard, then adjusts the rest of a recipe's flour and liquid to compensate.
How to Use the Sourdough Discard Calculator
Reference Values
The Science Behind It
Most sourdough starters are maintained at 100% hydration, meaning discard is roughly half flour and half water by weight. Accounting for this split keeps a recipe's overall flour-to-liquid ratio correct when discard is added. Source: King Arthur Baking.
King Arthur Baking's sourdough discard guidance confirms that most home starters are maintained at or near 100% hydration, making the roughly 50/50 flour-water split a reliable assumption for most discard-based recipe adjustments.
Discard recipes like pancakes and crackers benefit from the mild tang sourdough starter develops over time, a flavor characteristic distinct from the leavening power of active, recently fed starter.
Where This Shows Up
Home bakers maintaining a sourdough starter regularly generate discard and use this calculator to incorporate it into everyday recipes like pancakes or crackers rather than throwing it away.
Bakers adapting a standard recipe to include discard rely on this tool to adjust the remaining flour and liquid so the final batter or dough hydration stays correct.
Zero-waste cooking communities frequently share discard recipes specifically to help sourdough bakers avoid throwing away starter during routine feeding, making this conversion a popular reference.
A Worked Example
Say a pancake recipe calls for 200g of sourdough discard. Assuming a typical 100% hydration starter, that breaks down to roughly 100g flour and 100g water already contributed by the discard — meaning the rest of the recipe's flour and liquid amounts should be reduced accordingly to avoid an overly wet batter.
Discard vs Active Starter
| Discard | Active Starter | |
|---|---|---|
| Rising power | Weak to none | Strong, near peak |
| Flavor | More tangy over time | Milder, fresher |
| Best for | Pancakes, crackers, flavor | Leavening bread |
Common Mistakes
- Adding discard to a recipe without adjusting the other flour and liquid amounts, which can make the final batter too wet.
- Assuming all starters are maintained at the same hydration percentage, when some bakers intentionally keep a stiffer or wetter starter.
- Using discard interchangeably with active starter in a recipe that specifically needs leavening power, since discard's rising ability is usually much weaker.
- Using very sour, over-fermented discard in a delicately flavored recipe, where its tang can overpower other ingredients more than expected.
- Using discard straight from the fridge without accounting for its cooler temperature, which can slow a recipe's rise time slightly compared to room-temperature discard.
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Frequently Asked Questions
Is sourdough discard the same as active starter?+
It's the same mixture, just not necessarily at peak activity. It still contributes flour and water weight to a recipe.
How much flour is in 100g of discard?+
About 50g, assuming a typical 100% hydration starter.
Can I use discard in any recipe that calls for flour and water?+
Not always directly, but it can often replace a portion of both with some recipe adjustment, especially in pancakes, crackers, and quick breads.
Does discard need to be fed before using in a recipe?+
No, discard recipes are specifically designed to use unfed starter that would otherwise be thrown away.
Can I refrigerate discard before using it in a recipe?+
Yes, discard keeps well refrigerated for a week or more, making it convenient to accumulate before using it in a larger discard recipe.