How it works: Discard is flour and water in a known ratio. Flour inside = discard ÷ (1 + hydration) and water inside = discard - flour inside, with hydration as a decimal. Those amounts come off the recipe's flour and liquid, so the totals, and the texture they give, stay the same. The limit is whichever runs out first: flour × (1 + hydration), or liquid × (1 + hydration) ÷ hydration. Milk is treated as if it were all water, which is close enough for most batters.

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A home for the jar’s leftovers

Every feed leaves you with discard: the portion of starter you remove before adding fresh flour and water. It is perfectly good food, just too much to keep. Stirring it into pancakes, crackers, muffins or waffles adds a gentle tang and uses it up, but tipping it straight into a recipe makes the batter wetter and heavier than the recipe expects.

This converter tells you how much of the recipe’s own flour and liquid to hold back so that the total stays exactly where it was. It is for anyone who bakes from ordinary recipes and wants to fold discard in without guesswork.

Discard is flour and water in disguise

At 100% hydration, 150 g of discard is 75 g of flour and 75 g of water. If you add it on top of a recipe, you have quietly added both. The fix is simple arithmetic: take the discard’s flour off the recipe’s flour and its water off the recipe’s liquid. The batter then has the same thickness, the same ratio of dry to wet, and it bakes the same way.

It also explains the limit. Once the discard’s flour equals all the recipe’s flour, or its water equals all the liquid, there is nothing left to take away.

How to use it

Enter Flour in the recipe by weight.
Enter Liquid in the recipe, also by weight. Water, milk and buttermilk all count. Recipe written in cups? Run it through the cups to grams converter first.
Enter Discard to add and Discard hydration. A starter fed one part flour to one part water is at 100%.

Under Use this you get the new Flour, Liquid and Discard amounts. Below them you see what the discard itself contains, the share of the flour that now comes from discard, and Most discard this recipe can take.

Pancakes with 150 g of discard

A pancake batter uses 250 g flour and 300 g milk. You have 150 g of discard at 100%. The converter shows:

Flour: 175 g
Liquid: 225 g
Discard: 150 g
Flour inside the discard: 75 g
Water inside the discard: 75 g
Share of the flour from discard: 30%
Most discard this recipe can take: 500 g

Mix the eggs, sugar, leavening and fat exactly as written, using 175 g flour and 225 g milk plus the discard.

Got a whole jar? Enter 600 g and the converter stops you with “This recipe can take at most 500 g of discard at this hydration.” Beyond that point there would be no flour left to swap.

A stiffer discard behaves differently. At 60% hydration the same 150 g brings 94 g of flour and 56 g of water, so the recipe needs 156 g flour and 244 g milk, and the most it can take drops to 400 g.

What discard does and does not do

Unfed discard adds flavour and acidity, not much lift. Quick breads still rely on their baking powder or soda, so leave those amounts alone. The acid in discard reacts with baking soda, which is part of why discard pancakes tend to be tender and slightly tangy. If you want a proper sourdough rise from active starter instead, the yeast to sourdough converter is the better route.

Practical pointers

Weigh milk instead of pouring it by volume. A millilitre of milk weighs a touch more than a gram, and weighing avoids the cup-to-gram fuzz.
Old discard is sharper. A week in the fridge makes it noticeably sour; fresh discard is mild.
Start around 25 to 50% of the flour from discard. Much more and some batters lose structure, even though the totals are right.
Stir discard into the wet ingredients first so it spreads evenly.
Keep the jar under control. The starter feeding calculator helps you feed smaller amounts so there is less to use up.

Discard questions

Does milk count as liquid even though it is not pure water?

For this purpose, yes. Milk is mostly water, and treating it as liquid keeps the batter consistency close enough for pancakes, muffins and quick breads.

Can I use discard straight from the fridge?

Yes. Let it warm a little if the recipe uses melted butter, so the butter does not seize into lumps.

Why is the maximum different when my discard is stiffer?

A stiff discard carries more flour than water, so it runs out the recipe’s flour sooner. The converter checks both flour and liquid and reports whichever limit comes first.

Will discard make my bake taste sour?

A little tang, mostly. The amount of discard and how long it sat in the fridge matter more than anything else. Use less, or fresher discard, for a milder result.