Dough Hydration Calculator Including Sourdough Starter

The formula

True hydration = (water + other liquids + starter water) ÷ (flour + starter flour) × 100

A starter at hydration h% is made of 1 part flour to h/100 parts water. So a starter's flour is its weight ÷ (1 + h/100), and the rest is water. For a 100% hydration starter, half is flour and half is water.

Worked example

King Arthur Baking's hydration guide works through a country-style sourdough loaf:

425 ÷ 550 = 77% hydration. Enter 500 g flour, 375 g water, 100 g starter at 100% and 11 g salt in the calculator to see the same result, with salt at 2% of total flour.

Ignoring the starter, the recipe would look like 75%. The difference matters more with larger amounts of starter or with stiff starters.

What counts as water

The same guide counts liquids like milk, tea, coffee, beer, wine, juice, kombucha or kvass as water. It does not usually count butter, eggs or fresh fruit in hydration for bread, although they do contain water and soften the dough. In an enriched dough like brioche, the listed hydration can look very low because the eggs and butter supply much of the moisture.

What counts as flour

Only milled grains: wheat flours of all kinds, rye, spelt and so on. Cocoa powder, milk powder, potato flakes and similar ingredients absorb water but are not counted as flour.

Reading the result

King Arthur Baking describes doughs around 60% as low hydration or stiff, and doughs often above 80% as high hydration or slack. With all-purpose flour, it notes that 75–85% will likely feel slack or sticky and 55–65% firm. Whole-grain flours absorb more water, so a whole wheat dough at 75% will feel noticeably firmer than an all-purpose dough at 75%.

Higher isn't automatically better. Wetter doughs can give a more open, moist crumb but take more skill to shape. Bagels, pretzels and braided loaves often work best at lower hydration.

Converting a recipe

1. Run the recipe through this calculator to find its true hydration and salt percentage.
2. Enter those percentages in the baker's percentage calculator with the flour or dough weight you want.
3. Adjust: when changing hydration by more than a few percent, King Arthur Baking suggests recalculating with baker's math so the other ratios stay intact.

Read more in our hydration guide.

Common questions

What is the hydration of 500 g flour, 375 g water and 100 g starter?

With a 100% hydration starter, the starter adds 50 g flour and 50 g water: 425 ÷ 550 = 77.3%.

How do I know my starter's hydration?

From how you feed it. Equal weights of flour and water (1:1:1, 1:2:2 and so on) give a 100% hydration starter. If you feed 100 g flour with 60 g water, it is 60%.

Does milk count as water?

King Arthur Baking's hydration guide treats milk, tea, coffee, beer, wine and juice as water for hydration, even though they contain some solids.

Do whole-grain flours change the calculation?

No, hydration is calculated the same way for any flour. But whole-grain flours absorb more water, so the same hydration feels firmer than with white flour.