Sourdough Hydration Calculator

What "hydration" actually means

In bread baking, hydration is the weight of water divided by the weight of flour, expressed as a percentage. A dough with 500 g of flour and 375 g of water is at 75% hydration. That single number — more than the recipe's name or the flour variety — predicts how the dough will feel in your hands, how open the crumb will be, and how long the bulk ferment should run. A stiff bagel dough sits at 55–60%. A supple sandwich loaf lives around 65%. Rustic sourdough boules run 72–80%. Very high-hydration ciabatta and focaccia climb to 80–90% or beyond.

The reason bakers use percentages instead of ratios is that percentages scale cleanly. If you know a recipe is 75% hydration and 2% salt, you can bake 500 g of flour or 5000 g of flour and the salt and water still land in the right proportion without touching a calculator. This system is called baker's percentages, and it's the language every serious bread book is written in.

Baker's percentages in one paragraph

The total flour in a recipe is always 100%. Every other ingredient is expressed as a percentage of that flour weight. Water is usually 60–85%. Salt is 1.8–2.2% for most breads. Fresh yeast is 1–2%, instant yeast about a third of that. Sourdough starter is 15–25% of the flour weight. To convert a percentage into grams, multiply by the flour weight and divide by 100: 2% salt on 500 g of flour is 500 × 2 ÷ 100 = 10 g. That's the whole system.

Why the starter counts (if you're being precise)

A 100% hydration starter — the standard fed 1:1:1 with flour and water — is exactly half flour and half water by weight. If your recipe calls for 500 g flour, 375 g water, and 100 g starter, the true totals are 550 g flour and 425 g water, which is 77% hydration, not the 75% you might have read off the recipe. That 2% difference is small enough that most home bakers ignore it, but at high hydrations (85%+) or with stiffer levains it matters. Toggle "include starter" above to see the difference; use it when you're troubleshooting a wet, slack dough that shouldn't be as slack as it feels.

Choosing a hydration to target

Higher isn't better; higher is different. As hydration climbs, the dough becomes more extensible, the crumb opens up with bigger irregular holes, and the crust crackles more. It also becomes harder to shape, ferments faster, and demands stronger flour with a higher protein content (12%+). If your loaves are dense and tight, moving from 70% to 75% often helps more than adding more starter. If your loaves spread flat and refuse to hold a shape, drop 3–5% off the hydration or move to a stronger flour before you blame your technique.

The flour matters too

Whole wheat, rye, and freshly-milled flours absorb more water than white bread flour. A 75% hydration boule made with 20% whole wheat feels much stiffer than the same 75% dough made with 100% white flour, because the bran and germ pull in extra moisture during the autolyse. Bump the hydration by 3–5% when you swap 20–30% of the white flour for whole grain, and expect to keep bumping it as the whole-grain percentage climbs. Rye flour in particular can happily take on 85–90% water without feeling wet.