Sourdough Bread Calculator

Apparent hydration is the simplest way to think about your dough's wetness: the water you pour in divided by the flour you pour in. It ignores whatever flour and water are hiding inside your starter. Most home recipes and YouTube tutorials use this number, and it is the default in this calculator.

True hydration counts everything, including the flour and water your starter contributes. A 100% hydration starter is half flour, half water, so adding it pushes the real water-to-flour ratio up slightly. Professional bakers and textbooks typically use true hydration because it reflects the actual dough consistency.

For example, if you mix 500g flour + 335g water + 100g of 100% hydration starter, apparent hydration is 335 / 500 = 67%. The starter adds 50g flour and 50g water, so true hydration is (335 + 50) / (500 + 50) = 385 / 550 = 70%. Switch the calculator to advanced mode and the toggle at the top lets you work in whichever framing you prefer, with both shown in the results. Simple mode sticks to apparent hydration, which is the one home recipes use.

Your starter (also called a "mother" or "culture") is the ongoing colony of wild yeast and bacteria you keep alive in a jar by feeding it flour and water. You never put the whole thing into a recipe.

A levain (sometimes spelled "leaven") is a small offshoot you build from a spoonful of your starter the night before or morning of your bake. You mix that spoonful with fresh flour and water, let it ferment until it peaks, and then fold it into your dough. The levain is what actually goes into your bread; the starter stays in the jar for next time.

These are two ways to express the same thing: how much levain goes into your dough.

Starter % is the total levain weight as a percentage of total flour. If your recipe calls for 20% starter and you have 500g of flour, you add 100g of levain. This is how most home recipes are written and is the default view in the calculator.

Prefermented flour % (PFF) tells you what fraction of your total flour was fermented inside the levain. With a 100% hydration levain, PFF is exactly half the starter percentage (because the levain is 50/50 flour and water). So 20% starter at 100% hydration = 10% prefermented flour.

PFF is more useful when you change the levain hydration. A stiffer levain (lower hydration) has more flour per gram, so the same PFF produces less total levain weight. The calculator converts between the two automatically when you switch the toggle.

A feeding ratio like 1:2:2 means 1 part ripe starter, 2 parts flour, 2 parts water. The ripe starter also contributes flour and water, so both the ratio and seed hydration determine the final levain hydration. With a 100% hydration seed, a 1:2:1 ratio makes a stiffer 60% hydration levain.

Higher-hydration levains ferment faster and produce a milder, more lactic flavor. Stiffer levains take longer but develop a more pronounced acetic (vinegary) tang. The ratio also affects how quickly the levain peaks, which matters for your bake schedule.

This is the two-feed routine we use to wake up a refrigerated starter before mixing dough. It begins two nights before the bake:

We keep ours at 90% hydration, sometimes described as a slightly stiff or lower-hydration starter. That means the water weighs 90% as much as the flour, so it stays a little firmer than a standard 100%-hydration starter. We casually call the feeds 1:2:2 and 1:1:1, but the exact ratios below use the order starter:flour:water.

1. First feed: Take the starter straight from the fridge and feed it at 1:2:1.8 — 1 part starter, 2 parts flour, and 1.8 parts water. We refer to this as our 1:2:2 feed. Use 85–90°F water, then leave it overnight in a proofer set to 80°F.
2. Morning feed: First thing the next morning, feed it again at 1:1:0.9. This is the feed we call 1:1:1, with just a little less water than flour. Use 85–90°F water and return it to the 80°F proofer for 3–4 hours.
3. Mix the dough: Use the starter when it is active and at or near its peak. The 3–4 hour window is our usual timing; the starter’s rise and activity are the final check.

Once the starter is ready, this is the mixing process we use before bulk fermentation:

1. Combine the recipe’s water, active starter, and flour in the mixer bowl.
2. Mix with the paddle attachment for 30–60 seconds, just long enough to bring everything together.
3. Let the dough rest for the fermentolyse. This rest includes the starter but not the salt.
4. Lightly spritz the top of the dough with water, add the salt, and spritz with a little more water.
5. Switch to the dough hook and mix for 60 seconds.
6. Move the dough to the proofing container, then place the container in the proofer set to 80°F for bulk fermentation.

Every ingredient is expressed as a percentage of the total flour weight. Flour is always 100%. If you use 67% water, that means 67g of water for every 100g of flour (or 335g for 500g flour).

This system makes scaling easy: double the flour, double everything else, and the dough behaves the same way. It also lets you compare recipes at a glance regardless of batch size.

The single biggest reason a recipe works for someone else and fails for you is the flour. A video shot with 12.7% protein bread flour at 75% hydration will give you a slack, spreading dough if your bag is 10.5% all-purpose. Pick your flour type in the calculator and it will suggest a starting hydration that suits it.

Here is the part that surprises most bakers: protein alone does not tell you how much water a flour drinks. It only works within refined wheat. Across different grains the relationship flips. Einkorn carries the most protein of any flour in the calculator, around 16%, and yet absorbs roughly 12% less water than bread flour, because its gluten is fragile and poorly hydrating. Rye is the mirror image: it has little gluten protein, around 9.5%, but drinks about 8% more water, because its absorption comes from pentosans rather than gluten. Pentosans make up only 2 to 3% of flour but hold 8 to 15 times their own weight.

That is why the calculator asks for a flour type first and treats the protein number as a refinement. The type carries the physics; the protein percentage separates all-purpose from bread flour from high-gluten, which is exactly the range where protein is a reliable signal.

Protein also moves things other than water. Stronger flour needs longer mixing to develop, tolerates more folds, and gives you a wider window before it over-proofs. Weaker flour wants a shorter mix, gentler handling, and an earlier stop on bulk. Whole grain ferments noticeably faster because the bran carries more enzymes and microbes. In advanced mode, open “How this flour changes your bake” to see the numbers for your blend.

US nutrition labels round protein to the nearest whole gram per 30g serving. A bag reading 4g could be anywhere from 11.7% to 15.0% protein, which spans all-purpose through high-gluten. Typing 13.3% from that panel is false precision.

Nutrition labels also use a different nitrogen conversion factor than millers do (6.25 versus 5.7 for wheat), so a label tends to read about 10% higher than the miller’s own number for the same flour. The number on the front of the bag or on a miller’s spec sheet is the one to trust. In advanced mode, the calculator’s protein input has a Nutrition Facts mode that takes grams and shows you the range it really means.

The hydration suggestions are a starting point, not a target. Two flours with identical protein percentages can behave very differently depending on gluten quality, and every sack of flour varies by lot. Always adjust by feel.

• Water absorption by flour type: sourdoughhydration.com, cross-checked against King Arthur and Caputo specifications
• Protein reference values and salt guidance: King Arthur Baking
• Dough development time by flour strength: Domson Academy
• Water distribution across starch, protein and pentosans: Bushuk, W. (1966), Bakers Digest 40(5):38; component absorption via BAKERpedia (Solvent Retention Capacity, AACC 56-11.01)
• Loaf volume and protein: Park et al. (2006), Cereal Chemistry 83(4):418–423