Sourdough Discard Recipe Calculator
Enter the flour and replaceable liquid from the original recipe, then enter the discard you want to use. The calculator separates the discard into flour and water so you can adjust the recipe by weight.
Maximum usable discard700
- Flour contributed by discard
- 50
- Water contributed by discard
- 50
- Flour to add
- 450
- Liquid to add
- 300
- Original flour replaced
- 10%
- Preserved recipe hydration
- 70%
- Conversion status
- Fits: add the listed flour and liquid to preserve the original totals.
Assumes the discard contains only flour and water.
Negative flour or liquid means the entered discard amount is above the maximum for an unchanged recipe.
How to use this calculator
- Weigh the flour in the original recipe and enter the total grams.
- Enter only the liquid that can realistically be reduced when discard is added.
- Enter the discard weight and its hydration percentage.
- Use the adjusted flour and liquid amounts, and check the status before baking.
How the discard conversion is calculated
Sourdough discard is not a separate ingredient for this purpose; it is already a mixture of flour and water. To add it without changing the main flour and liquid totals, the calculator decomposes the discard using baker's percentage hydration.
Let F be the original flour, W be the replaceable liquid, D be the discard weight, and H be discard hydration as a percent. Convert hydration to a decimal with h = H / 100. The flour inside the discard is Fd = D / (1 + h), and the water inside it is Wd = D * h / (1 + h).
The adjusted recipe is then simple subtraction: flour to add = F - Fd and liquid to add = W - Wd. A 100 g portion of 100% hydration discard contains 50 g flour and 50 g water. A 150 g portion of 50% hydration discard contains 100 g flour and 50 g water, because the flour weighs twice as much as the water.
Maximum discard without changing the totals
The maximum usable discard is limited by whichever original ingredient runs out first. The flour limit is Df = F * (1 + h). The liquid limit is Dw = W * (1 + h) / h. The calculator reports Dmax = min(Df, Dw). If the discard amount is at or below that number, both adjusted ingredients stay at zero or above.
If the discard amount is above the maximum, the calculator still shows the arithmetic instead of clamping the result. A negative liquid amount means the discard contributes more water than the recipe's replaceable liquid can absorb. A negative flour amount means the discard contributes more flour than the recipe originally had. In either case, use less discard or rebalance the recipe deliberately.
What changes the result most
Hydration changes the split between flour and water. Wet discard is usually limited by the liquid in the recipe; stiff discard is more likely to be limited by the flour. The recipe's original hydration, 100 * W / F, also matters because a dry dough or batter has less replaceable liquid available.
What this calculator leaves out
The calculation preserves flour and replaceable liquid by weight only. It does not preserve acidity, gluten development, flavor, fermentation time, salt level, sweetness, fat, or leavening. Milk, eggs, juice, oil, and other liquids contain solids, fat, sugar, or protein, so they may not behave like discard water gram for gram. Recipes written in cups should be converted to grams before using this tool.
Worked example
Suppose a recipe has 500 g flour and 350 g replaceable liquid, and you want to use 100 g of 100% hydration discard. The hydration decimal is 1, so the discard contains 100 / (1 + 1) = 50 g flour and 100 * 1 / (1 + 1) = 50 g water.
Subtract those from the original recipe: add 450 g flour and 300 g liquid. The discard replaces 10% of the original flour, and the preserved recipe hydration is 70%. The maximum usable discard is the smaller of 500 * (1 + 1) = 1000 g by flour and 350 * (1 + 1) / 1 = 700 g by liquid, so the limit is 700 g.
Common questions
How do I add sourdough discard to an existing recipe?
Weigh the flour and the replaceable liquid in the original recipe. Enter those weights, then enter the discard weight and hydration. Use the calculator output to reduce the added flour and liquid by the amounts already present in the discard.
How much flour and water are in 100% hydration discard?
At 100% hydration, the water weight equals the flour weight. That means 100 g of discard contains 50 g flour and 50 g water, while 200 g contains 100 g flour and 100 g water.
Can I use discard that is not 100% hydration?
Yes. Enter the actual hydration of the discard, not the hydration you wish it had. Stiff discard contributes more flour than water, and liquid discard contributes more water than flour.
What is the maximum discard I can add without changing the recipe?
The maximum is the smaller amount allowed by the original flour and the replaceable liquid. Above that limit, either the adjusted flour or adjusted liquid becomes negative, which means the original totals cannot be preserved by subtraction alone.
Can discard replace milk, eggs, oil, or other liquids?
Sometimes it can replace part of the water-like portion, but it is not a gram-for-gram match for every liquid. Milk, eggs, oil, juice, and syrups bring solids, fat, protein, sugar, or emulsifiers. Treat those substitutions as recipe development, not just hydration math.
Does sourdough discard replace baking powder or yeast?
Usually no. Discard may have acidity and flavor, but it is often not strong enough or predictable enough to replace a leavener. Keep the recipe's baking powder, baking soda, or yeast unless you are intentionally redesigning the recipe.