Sourdough Hydration Calculator

Why starter changes hydration

A sourdough starter is flour and water that already fermented. If you ignore it, a dough that looks like 70% hydration on the bowl water alone is wetter (or drier) than you think once the starter's water and flour join the mix.

This calculator adds starter flour and starter water to the dough totals, then reports one dough hydration. The default starter is 100% hydration: equal parts flour and water by weight.

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How to use this calculator

Enter flour in the final dough, water you add to that dough, starter grams, and the starter's own hydration percent. Defaults are 500 g flour, 350 g water, 100 g starter, 100% starter hydration.

The result labeled dough hydration includes the starter. Total flour and total water are printed so you can write an overall baker's percent next to the baker's percentage tool.

If your jar is marked "1:1:1" feed (starter:flour:water by weight), that feed is 100% hydration on the new flour, and the whole jar stays near 100% if it started there. Type 100 unless you keep a stiff starter on purpose.

Zero starter is allowed. Then hydration collapses to bowl water over bowl flour, the same number as the baker's percentage page. Use this page when the jar is going in the dough.

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Formula and worked example

Starter flour = starter ÷ (1 + starter hydration as a decimal). Starter water = starter − starter flour. Dough hydration = (water + starter water) ÷ (flour + starter flour) × 100.

With the defaults, starter hydration is 1.00. Starter flour is 100 ÷ 2 = 50 g. Starter water is 50 g. Hydration is (350 + 50) ÷ (500 + 50) × 100 = 400 ÷ 550 × 100 = 72.7%.

If you had reported only bowl water over bowl flour, you would have called that dough 70% and been 2.7 points low.

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What 100% starter hydration means

A 100% starter is maintained with equal weights of flour and water. A stiff 50% starter is two parts flour to one part water. A loose 125% starter is more water than flour.

Change the starter hydration field when your jar is not 1:1. The split math still holds. A 200 g stiff 50% starter contributes 200 ÷ 1.5 = 133.3 g flour and 66.7 g water.

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Target dough hydrations after the starter is included

Many pan sandwich loaves sit near 65% to 72% once starter is counted. Higher hydration country loaves need stronger flour and more folds.

Whole-wheat and rye drink more water. A 75% number that feels slack on white flour can feel tight on a 50% whole-grain mix. Adjust water, then re-run the calculator so the notebook matches the bowl.

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Overall baker's percent after the split

Professional references call the recomputed percents overall baker's percent. Salt should be based on total flour, including starter flour, or the loaf tastes under-salted when inoculation is high.

Example from the defaults: total flour 550 g. For 2% salt on total flour, use 11 g salt, not 10 g on the 500 g bowl flour alone. This widget does not compute salt. Do that on the baker's percentage page with total flour as the flour input.

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Inoculation (how much starter relative to flour)

Inoculation is starter flour as a percent of total flour, or sometimes starter mass as a percent of dough flour. Using the defaults, starter flour is 50 g of 550 g total, about 9%. A 20% inoculation (more starter flour) ferments faster in a warm kitchen.

Kids' weekend bake schedule often wants a same-day loaf. Raise inoculation or room temperature rather than dumping extra water. Water changes dough feel more than it speeds acid production.

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Measuring a lively starter

Stir the jar, then weigh. A hooch layer on top is mostly water and alcohol. If you pour only hooch, you are not adding the flour the formula expects.

Feed with the same flour you will bake with when you can. A rye-fed starter adds rye flour to the total flour number even if the dough flour field is all white.

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Bake-out and leftover bread

Sourdough acidity does not make raw dough safe to eat. Flour still needs a full bake. FDA raw-dough guidance applies.

Cool loaves, then store. USDA leftover rules still apply to filled or meat-topped sourdough pizzas and grilled cheese: 2 hours at room temperature, 165 °F to reheat leftovers.

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Two hydrations from one bowl, and which to trust

Bowl hydration (water you poured ÷ flour you poured) is a mixing convenience. Dough hydration (all water ÷ all flour) is the number that predicts feel after the starter disappears into the mass.

Keep both numbers in a notebook for a month. You will see that a 20% inoculation of 100% starter lifts a 70% bowl dough into the mid-70s. That lift is why a "70% recipe" copied from a no-starter loaf feels wetter when you convert it to sourdough without cutting bowl water.

To hold dough hydration at 70% with the default 100 g of 100% starter and 500 g dough flour, you need bowl water W such that (W + 50) / 550 = 0.70. W + 50 = 385, so W = 335 g, not 350 g. The widget will read 70.0% if you type 335.

Kids who want a taller sandwich loaf should aim for the 65% to 70% dough-hydration band and a tin, not a wet 80% free-form boule. High hydration is a skill tax, not a flavor requirement.

If the starter is very ripe and watery, the labeled jar hydration may be a lie. Stir, weigh a spoon of it, dry it in a low oven on parchment, and weigh the dry flour if you want a true split. Most home bakers skip that and accept a 1 or 2 point error.

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A weekend schedule that matches the hydration number

A 72.7% dough from the defaults is slack enough to need folds. Plan those folds in the first two hours after mix, then an overnight fridge rest if Saturday morning is for soccer.

Cold dough feels drier. Do not add water in the morning because the fridge dough looks stiff. Let it warm 30 to 40 minutes on the counter, then shape. The hydration number did not change overnight. The butter-soft feel comes back with temperature.

Kids can do the folds with wet hands. Wet hands are water you did not enter. A few droplets are noise. A child rinsing hands into the bowl is a new hydration. Watch the bowl, not only the scale.

Salt still wants to be about 2% of total flour. On 550 g total flour that is 11 g. If you already put 10 g in when you thought flour was 500 g, you are at 1.8% of total flour. Edible, a little flat. Add a gram next time rather than sprinkling salt on the crust.

Whole-rye starter in a white dough adds rye flavor and a little extra absorbency. Put the rye grams into the flour field if you know them, or accept that the printed hydration is a white-flour approximation.

Do not chase "open crumb" photos at 82% if you need sandwich slices for lunchboxes. A 68% tin loaf cuts cleaner and wastes less. Hydration is a lunch problem as much as an Instagram problem.

If the starter smells like nail polish or sits ignored for a month, feed it to strength before you trust a hydration number. Dead starter does not change the split math. It changes whether the loaf rises.

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Limits

The math assumes the starter is only flour and water at the hydration you typed. Add-ins (honey, milk, mashed potato) are extra water or sugar the formula does not see.

Discard weight is not the same as ripe starter weight. Use the starter you mix into the dough, not the amount you threw away yesterday.

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How it works

A 100% hydration starter is equal parts flour and water by weight. Ignoring starter undercounts both flour and water.

Frequently asked questions

• What hydration for sandwich bread?

  Many pan loaves sit near 65 to 72% once starter is included.

Related calculators

References

1. King Arthur Baking. Baker's Percentage (preferments and overall percent)
2. King Arthur Baking. Professional baker's reference: preferments
3. USDA. FoodData Central
4. FDA. Raw dough
5. USDA FSIS. Leftovers and food safety
6. USDA FSIS. Safe minimum internal temperature chart
7. USDA Ask FSIS. 2 Hour Rule
8. USDA FSIS. Danger Zone (40 °F to 140 °F)