Sourdough

Sourdough Discard Calculator

Enter your discard weight and hydration to see the exact flour and water it contains — then get substitution amounts for pancakes, crackers, waffles, pizza, and more.
Flour split exact grams at any hydration 6 recipes substitution amounts 50–200% hydration range
Sourdough starter discard in a glass jar ready for use in a recipe

Auto-calculates as you type

Flour equivalent 75 g
Water equivalent 75 g
Total discard 150 g
Flour-to-water ratio 50:50
Flour 75 g Water 75 g
Flour Water

Recipe substitutions — using 150 g of discard

Recipe Replace flour Replace liquid Tip
🥞 Pancakes 75 g flour 75 g milk/water Replace equal weights of flour and liquid with the discard.
🧇 Waffles 75 g flour 75 g liquid Works like pancakes — swap flour and liquid 1:1 by weight.
🫙 Crackers 75 g flour No liquid swap needed Mix discard with olive oil and salt, roll thin, and bake at 180°C until crisp.
🍕 Pizza dough 75 g flour 75 g water Adds tang and chew. Add commercial yeast for a reliable rise.
🍌 Banana bread 60 g flour No liquid swap Stir up to 120g of discard into the batter — reduces flour and adds depth.
🧁 Muffins 50 g flour 50 g liquid Replace up to 100g discard for flour + liquid in your favourite muffin recipe.

Flour and water amounts reflect the actual composition of your discard at 100% hydration. Adjust your recipe's other wet/dry ingredients to compensate. Results are estimates — taste and texture will vary with starter age and flour type.

Flour & water content per 100 g of discard — by hydration

Hydration Flour Water Best for
50% 67g 33g Stiff — adds body to crackers, stiff doughs
75% 57g 43g Medium — versatile in most recipes
100% 50g 50g Standard — equal split, easiest to calculate
125% 44g 56g Wet — more liquid than flour; good for batters
150% 40g 60g Very wet — thin batters, waffles, crêpes

Exact splits: flour = discard ÷ (1 + hydration/100), water = discard − flour.

Sourdough discard guide

Stop binning it. Start baking with it.

Sourdough discard is just unfed starter — still flavourful, still active enough to transform pancakes, crackers, and pizza dough. This guide shows you the science behind the substitution, what discard is really made of, and how to use every gram.

100% hydration 50 / 50

Equal flour and water per 100g. The most common starter type — easy to substitute.

Best use: fresh 1–7 days

Mild, balanced tang. Use within a week for pancakes, waffles, and banana bread.

Best use: aged 1–2 weeks

Sharper, more complex flavour. Excellent for sourdough crackers and pizza.

The split formula Flour = discard ÷ (1 + H)

Where H is hydration as a decimal (e.g. 1.0 for 100%). Flour in 150g of 100% discard = 150 ÷ (1 + 1.0) = 75g. Water = 150 − 75 = 75g. The calculator applies this automatically for any hydration level.

01

How to use this sourdough discard calculator

Enter the weight of discard you have in grams, then set your starter hydration using the slider. The calculator immediately shows the flour and water inside that discard and generates a substitution table for six common recipes. To use the substitution: reduce the flour and liquid in your recipe by the amounts shown, then stir in the discard to replace them.

If you are not sure of your hydration, most home bakers maintain a 100% hydration starter (equal parts flour and water by weight). If your starter is thicker or wetter than that, adjust the slider accordingly.

02

What is sourdough discard?

Discard is the portion of starter you remove before each feeding. Every time you feed your starter, you add fresh flour and water in a set ratio — but first you remove a portion to prevent the jar from overflowing and to keep the acidity within the range where yeast thrives. That removed portion is called discard.

Discard is not dead starter. It still contains billions of wild yeast cells and lactic acid bacteria, just in a more acidic and less actively rising state. This makes it perfect for adding flavour to quick breads, batters, and flatbreads where a chemical leavener handles the rise.

03

The flour-to-water split explained

Every gram of sourdough discard is a mixture of flour and water. The exact split depends on your starter's hydration percentage. At 100% hydration, your discard is exactly half flour and half water by weight — 150g of discard contains 75g of flour equivalent and 75g of water equivalent. At 75% hydration, the same 150g holds about 86g of flour and 64g of water.

This matters when you substitute discard in a recipe. If you stir 150g of 100% hydration discard into pancakes without adjusting the recipe, you are adding 75g of extra flour and 75g of extra liquid. The calculator shows you exactly what to reduce so the batter comes out at the right consistency.

Example: 150g of 100% hydration discard in pancakesFlour equivalent: 75g — reduce your recipe flour by 75gWater equivalent: 75g — reduce milk or water by 75gNet result: same batter weight, same texture, added tang
04

Using discard in pancakes and waffles

Pancakes are the most popular use for sourdough discard because the recipe is forgiving and the discard genuinely improves the result. The wild yeast acids in the discard react with baking soda or baking powder to create extra lift, and the lactic acid tenderises the gluten in the batter, producing a softer, more pillowy texture than plain flour pancakes.

To swap discard into your favourite pancake recipe, use the substitution amounts from the calculator above. Reduce the flour and liquid by the corresponding amounts, then add the discard. Mix until just combined — do not overmix or you will develop too much gluten. The batter will look slightly thicker than usual before cooking; a small rest of 5 minutes allows the discard to hydrate fully.

05

Discard crackers, pizza dough, and quick breads

Sourdough crackers are arguably the most impressive thing you can make with discard, requiring almost no recipe. Mix discard with olive oil, salt, and any seeds or herbs you like, spread it thinly on baking paper, score into rectangles, and bake at 180°C for 20–25 minutes until golden and crisp. The acidity of the discard gives the crackers a complex flavour that rivals store-bought versions.

In pizza dough, discard adds tang and a slightly chewy crumb. Because discard is too weak to leaven dough on its own, always add a small amount of commercial yeast alongside it. Use the discard as a partial flour-and-water replacement (the calculator shows the exact amounts), mix and knead as normal, then let it rise for 1–2 hours before baking. For banana bread, muffins, and similar quick breads, simply stir up to 100–120g of discard into the batter — it replaces a portion of flour and milk and adds a subtle depth of flavour.

06

How to store sourdough discard safely

Discard keeps best in a sealed glass jar in the fridge. Every time you feed your main starter, scrape the removed portion into the jar and top it up. Label the jar with the date you started it. Over time the discard will become progressively more sour as the bacteria continue working at cold temperatures.

For the mildest flavour, use discard within one week. For crackers and savoury applications where tang is an asset, two-week-old discard works well. Beyond two weeks the smell becomes sharp (sometimes acetone-like) — the discard is usually still safe but very acidic. When in doubt, start fresh.

1–3 daysVery mild, close to fresh starter. Ideal for delicate recipes like crepes.
4–7 daysBalanced tang. Best for pancakes, waffles, muffins, and banana bread.
1–2 weeksMore sour. Excellent for crackers, pizza, and sourdough flatbreads.
2+ weeksSharp, pungent. Still usable in heavily flavoured savoury recipes.
Smells like acetoneDominant acetic acid. Use small amounts in strong-flavoured recipes or discard.
07

Discard vs unfed starter — is there a difference?

Discard and unfed starter are the same thing. Discard is the name used when you remove starter as part of the feeding process. Unfed starter is just starter that has not been fed recently — whether you intentionally set it aside or forgot about it. In both cases, the starter contains active cultures in an increasingly acidic environment.

The practical difference is timing. Fresh discard (removed right before or right after feeding) is at an earlier stage of fermentation. Very old discard that has sat unfed for days or weeks is at a much later stage. Both can be used in baking, but older discard is significantly more sour. Some bakers keep a separate "discard jar" in the fridge and add to it over several weeks, using the accumulated discard in large batches of crackers or pizza dough.

08

Tips for building a useful discard stash

If you bake frequently, a rolling discard jar is the most practical approach. Keep a 500ml or 1L jar in the fridge and add discard every time you feed your starter. Do not add fresh discard on top of very old discard without using some of the older batch first. A good rule is to use about half the jar before adding more, which keeps the average age balanced.

If you have more discard than you can use quickly, consider drying some of it. Spread a thin layer on baking paper, let it dry at room temperature for 24–36 hours until completely brittle, then break it into flakes and store in an airtight jar. Dried discard keeps for months and can be rehydrated with a little warm water to use in recipes.

Next Steps

Use these next

Use these next based on where you are in your bake right now.

Step 1 Sourdough Hydration Calculator Enter your total dough weight and hydration percentage to calculate exact flour and water weights for a sourdough formula. Open calculator → Step 2 Levain Calculator Build your levain precisely — flour blend, hydration level, starter percentage, and timing all in one. Open calculator → Step 3 Sourdough Starter Calculator Work out exactly how much starter, flour, and water you need for any recipe or feeding ratio. Open calculator →

Guides for this calculator

How to feed your sourdough starter Practical feeding routine for daily and weekly bakers. What is an active sourdough starter? Check readiness before mixing or feeding. Sourdough starter feeding ratios Pick the right ratio for schedule, strength, and flavor.

FAQs

Frequently Asked Questions

Common questions about sourdough discard — storage, substitutions, and hydration.

What is sourdough discard?

Sourdough discard is the portion of your starter you remove before each feeding. Without discarding, the culture would grow indefinitely and eventually become too acidic for the yeast to survive. Discard is simply unfed starter — it still contains live cultures but lacks the yeast activity needed to leaven bread on its own. It can be refrigerated and used in any recipe that calls for a chemical leavener like baking powder or baking soda.

Can I use discard straight from the fridge?

Yes. Cold discard can go directly into most batter-based recipes like pancakes, waffles, and muffins without any issues. For recipes that are more sensitive to temperature — like crackers baked very thin or pizza dough that needs to be stretched — you may want to bring it to room temperature first. Cold discard will also slow fermentation slightly if used in a yeasted dough.

How does discard hydration affect my recipe?

Hydration determines how much flour and water your discard contributes. A 100% hydration discard (equal weights of flour and water) adds equal amounts of both. A 75% discard contains more flour than water. This calculator works out the split automatically so you know exactly how much flour and liquid to reduce in your recipe when swapping in discard.

How long does sourdough discard keep in the fridge?

Discard keeps well in the fridge for 1–2 weeks in a sealed container. Over time it becomes more sour as the bacteria continue producing acetic acid at cold temperatures. Very old discard (over 2 weeks) can have a sharp, almost acetone-like smell — it is usually still safe to use in baked goods but will add pronounced acidity. For mild flavour, use discard within 1 week.

Can I use discard instead of baking powder?

No — discard cannot replace baking powder directly. Discard adds flavour, tenderness, and slight tang, but it does not have enough active yeast to leaven baked goods on its own. It works best combined with baking powder or baking soda in quick breads, pancakes, muffins, and crackers. In yeasted doughs like pizza, you can add discard alongside commercial yeast for flavour without relying on it for lift.

Why does my discard smell like acetone or nail polish?

An acetone or very sharp smell in discard usually means the acetic acid produced by bacteria has become dominant — this happens when the starter has gone too long without feeding or has been stored cold for an extended period. The discard is almost always still safe to use, but the baked result will taste very sour. Feed your main starter more frequently and use fresh discard within a week for a milder flavour.

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