How much discard can I put in a recipe?

It depends on the bake, which is why the calculator starts from a ratio rather than a fixed number. Pancakes, waffles, crackers and flatbreads take discard at about the weight of the flour. Muffins, scones and quick breads sit better at half the flour weight, and cookies, brownies and cakes at about a third. If your recipe already names an amount of discard, choose Custom and enter the grams it uses per 100 g of flour.

Is my discard really 100% hydration?

If you feed the way the starter guide does — equal weights of starter, flour and water at 1:1:1 — then yes: half the discard's weight is flour and half is water, so it is 100% hydration. A stiffer culture kept around 2:1:1 or a runny one that has separated will not be, so change the hydration field and the flour-and-water split moves with it.

Do I still need baking soda or baking powder?

Yes. Discard is acidic, so discard quick breads normally pair it with baking soda for lift, and the calculator does not touch leavening at all — it swaps flour and liquid only. Follow your recipe for the raising agents; if you are adapting a recipe yourself, adjust the leavening in the bake, not here.

Can I use discard straight from the fridge?

For chemically leavened bakes such as muffins, pancakes and cookies, cold discard is fine — it changes the timing of nothing that matters, and the swap arithmetic is the same either way. For anything raised by the starter itself, a cold starter needs longer, and the baking schedule calculator is the better place to plan that.

What happens if I have less discard than the ratio wants?

The calculator caps the swap at what is actually available and says so in the results, showing both the amount your ratio asked for and the amount it used. You can also hold less back for the next feed: the held-back amount is subtracted from the jar before the discard is counted, so lowering it frees up discard for the recipe.

Discard math

Sourdough Discard Calculator

Discard is flour and water you have already paid for. Tell the calculator how much is in the jar and what your recipe calls for, and it tells you how much discard to use, how much flour and liquid that discard replaces, what to add instead, and how much starter to keep back for the next feeding — in grams, with cups and spoons alongside.

Your jar and your recipe

Discard on hand (g)

Everything in the discard jar right now, before you take anything out.

Discard hydration (%)

A starter fed equal weights of flour and water — the everyday 1:1:1 feed — is 100%. Leave it at 100 if you feed like the starter guide does.

Starter to hold back for the next feed (g)

What stays in the jar so you still have a starter tomorrow. Enter 0 if every bit of the discard is going into the recipe.

Flour the recipe calls for (g)

The flour weight written on the recipe, before you swap any of it for discard.

Liquid the recipe calls for (g)

Water, milk, buttermilk or whatever the recipe pours in — weighed, not measured in cups, so the subtraction lines up.

Discard to flour (discard : recipe flour)

1:1Discard weighs the same as the flour. Pancakes, waffles, crackers and flatbreads.1:2Half the flour weight. Muffins, scones and quick breads.1:3A third of the flour weight. Cookies, brownies and cakes.CustomSet your own grams of discard per 100 g of flour below.

Your numbers

Add your discard, your recipe's flour and liquid, and press Calculate the swap. The adjusted amounts appear here.

How the discard calculator works

Discard is unfed starter, so it is flour and water that is already mixed. Once you know how much of it the recipe can take, the flour and water it carries come out of the recipe's own flour and liquid — the swap is a subtraction, not a guess:

Discard available = discard on hand − starter held back for the next feed
Discard to use = recipe flour × (grams of discard per 100 g of flour ÷ 100)
Flour in that discard = discard used ÷ (1 + hydration ÷ 100)
Water in that discard = discard used − the flour in it
Flour to add = recipe flour − the flour the discard brings
Liquid to add = recipe liquid − the water the discard brings

Worked example. You have 300 g of discard and you hold 100 g back, so 200 g is available. A muffin recipe calls for 240 g of flour and 240 g of milk, and you pick 1:2 — discard at half the flour weight. The calculator uses 120 g of discard, which brings 60 g of flour and 60 g of water, so you add 180 g of flour and 180 g of milk. That leaves 80 g of discard for another day, and the 100 g you held back gets fed 100 g of flour and 100 g of water at 1:1:1.

Which discard ratio should you pick?

Discard : flour	What that means	Usually used for
1:1	100 g discard per 100 g flour	Pancakes, waffles, crackers and flatbreads — batters that want a real tang and can take the extra liquid.
1:2	50 g discard per 100 g flour	Muffins, scones and quick breads — enough discard to taste it, not so much that the crumb turns dense.
1:3	about 33 g discard per 100 g flour	Cookies, brownies and cakes, where the fat and sugar carry the flavour and a little discard is plenty.

These are starting points for the bakes discard usually ends up in, not rules. If your recipe already names an amount of discard, choose Custom and enter the grams it asks for per 100 g of flour — or leave the ratio and the recipe as written and treat the numbers here as the check.

What the numbers do not do

Leavening is yours to handle. Discard is acidic, so discard quick breads usually pair it with baking soda for lift. The calculator swaps flour and liquid only — follow your recipe for the raising agents.
Cups and spoons are approximate. The gram weights are the exact answer; the volume line assumes 120 g of flour per US cup and 236 g of water per US cup. A scale beats a scoop every time.
The hydration field matters. A runny starter at 125% brings more water and less flour than a thick one at 75%, so the split changes even when the discard weight does not.
Arithmetic is not diagnosis. If the discard smells sharp, has gone watery or has changed colour, the sums will still be right and the jar still needs a look. Those pages are linked below.

Sourdough discard questions

How much discard can I put in a recipe?: It depends on the bake, which is why the calculator starts from a ratio rather than a fixed number. Pancakes, waffles, crackers and flatbreads take discard at about the weight of the flour. Muffins, scones and quick breads sit better at half the flour weight, and cookies, brownies and cakes at about a third. If your recipe already names an amount of discard, choose Custom and enter the grams it uses per 100 g of flour.
Is my discard really 100% hydration?: If you feed the way the starter guide does — equal weights of starter, flour and water at 1:1:1 — then yes: half the discard's weight is flour and half is water, so it is 100% hydration. A stiffer culture kept around 2:1:1 or a runny one that has separated will not be, so change the hydration field and the flour-and-water split moves with it.
Do I still need baking soda or baking powder?: Yes. Discard is acidic, so discard quick breads normally pair it with baking soda for lift, and the calculator does not touch leavening at all — it swaps flour and liquid only. Follow your recipe for the raising agents; if you are adapting a recipe yourself, adjust the leavening in the bake, not here.
Can I use discard straight from the fridge?: For chemically leavened bakes such as muffins, pancakes and cookies, cold discard is fine — it changes the timing of nothing that matters, and the swap arithmetic is the same either way. For anything raised by the starter itself, a cold starter needs longer, and the baking schedule calculator is the better place to plan that.
What happens if I have less discard than the ratio wants?: The calculator caps the swap at what is actually available and says so in the results, showing both the amount your ratio asked for and the amount it used. You can also hold less back for the next feed: the held-back amount is subtracted from the jar before the discard is counted, so lowering it frees up discard for the recipe.

Where to go next

If the numbers left you with discard to spare, thestarter feeding calculatorworks out the next feed in full, and thecups to grams convertercovers any ingredient this swap did not touch. Scaling the rest of the recipe is therecipe scaling calculator.

A starter that has gone quiet, pours instead of holding its shape, or bubbles without rising needs a fix rather than a formula — start withbubbling but not rising orfixing a watery starter.