Hydration percentage shows up on every recipe card, but most bakers use it as a rough label rather than the precise ratio it actually is. Get the formula right and the number stops being trivia — it becomes a direct lever on crumb structure, dough handling, and how fast your bake moves.
Baker's percentage hydration is simple: total water weight divided by total flour weight, multiplied by 100. Every ingredient is expressed as a percentage of the total flour weight, and flour itself is always 100%.
The part that trips people up is the starter. A mature sourdough starter is itself a mix of flour and water — usually close to 100% hydration if it's fed 1:1:1. That means the starter contributes to both totals, not just the water side. Leave it out and your hydration math will be quietly wrong on every bake.
The same logic applies to any other flour-and-water addition — a soaker, a poolish, a scalded portion of flour. Add its flour to the flour total and its water to the water total before dividing.
It's worth doing this math once by hand rather than trusting a recipe's stated percentage blindly. Recipes are written inconsistently — some authors fold the starter into the totals correctly, some quietly ignore it, and some calculate hydration on "flour added at final mix" only, excluding any pre-ferment entirely. None of these are wrong as conventions, but they aren't interchangeable, and comparing two recipes' hydration numbers only makes sense if both were calculated the same way. When in doubt, add up every gram of flour and every gram of water in the formula, starter included, and divide. That number is the one that actually describes how the dough will feel in your hands.
Water content changes dough behavior on three fronts, and they all move together.
Crumb. Higher hydration gives more mobile gluten strands and more room for gas cells to expand unevenly, which produces the open, irregular crumb with large holes associated with artisan bread. Lower hydration constrains that expansion, giving a tighter, more uniform crumb — the texture you want in a sandwich loaf that has to hold a slice of cheese without tearing.
Handling. Wetter dough is stickier and slacker. It spreads more before it sets, and it generally needs more gluten development — more folds, more careful shaping — to hold any shape at all during proofing. Drier dough is easier to handle from the start: it holds its shape better through shaping, proofing, and the oven, though push hydration too low and the crumb turns dense and tight rather than merely uniform.
The handling difference is why hydration and skill level tend to travel together. A 65% dough forgives an imprecise fold, a slightly under-developed gluten network, or a few extra minutes on the bench before shaping — it simply holds together. Push the same recipe to 80% and every one of those small lapses shows up as a flat loaf or a dough that won't hold a boule shape. This is a practical argument for raising hydration gradually rather than a purity argument about "real" sourdough — a wetter dough is not inherently better bread, just a different set of trade-offs.
Gluten strength required. More water means the gluten network has to do more work to trap the same volume of gas across a more mobile matrix. That's why high-hydration formulas lean so heavily on stretch-and-fold or coil-fold sequences during bulk fermentation rather than a single intensive knead up front — repeated folding builds strength incrementally as the dough relaxes, which suits a slack dough better than aggressive kneading does.
Fermentation speed. This one is less obvious but real — see the fact box below.
These are typical starting points, not fixed rules — flour, technique, and personal preference all shift them:
These ranges aren't targets to hit precisely — they're a sanity check. If a rustic boule recipe calls for 95% hydration, that's a signal to look closely at the technique before committing flour and time, not necessarily a mistake. Some bakers do work at extreme hydrations deliberately, but it requires matching mixing method, fold schedule, and often flour choice to the water level, not just adding more water to a standard formula.
The same hydration number behaves differently depending on the flour. Whole wheat and rye absorb noticeably more water than white bread flour, because of the bran content and a different starch structure. A whole-grain dough mixed at "70%" will feel drier and stiffer at first mix than a white-flour dough at the same percentage — more like a 60–65% white dough — because the bran is still soaking up water it hasn't fully absorbed yet.
Two practical responses to this: give whole-grain doughs a rest (an autolyse) before you judge how wet they feel, since absorption continues for 20–30 minutes after mixing; or add water gradually as the bran hydrates, rather than committing to a fixed number upfront. Substituting whole wheat or rye into a recipe originally written for white flour, at the same stated hydration, is one of the more common reasons a dough turns out drier and denser than expected — the percentage stayed the same, but the flour's water demand didn't. For the full breakdown of how different flours absorb water and behave in fermentation, see our flour types article rather than re-deriving it here.
Change hydration in small steps — 2 to 5 percentage points at a time — rather than jumping from a familiar 65% straight to an ambitious 85%. The reason isn't just feel: your technique has to catch up with the wetter dough. Fold frequency, shaping approach, and even your sense of "properly proofed" all shift as water content rises, and a large jump usually produces a dough you don't know how to read yet.
One way to push hydration higher without losing early gluten development is bassinage — holding back a portion of the water at initial mix and adding it gradually once the gluten network has started to form. It lets you reach a wetter final dough than mixing all the water in at once would comfortably allow, because the gluten strands have already organized themselves before they're asked to hold extra water. We cover the technique in detail in our bassinage guide rather than repeating it here.
A practical way to test a new hydration level before committing a full batch: mix a small test dough — a few hundred grams — at the target percentage, and watch how it behaves through one fold cycle. If it's unworkable at that scale, it will be worse at full size. This costs a little flour but saves a bulk fermentation and a bake on a dough you were never going to be able to shape.
Hydration is one of the inputs S.D Timer factors into your bake schedule alongside temperature and inoculation ratio, since a wetter dough moves through bulk fermentation a bit faster than a stiffer one at the same temperature.
📅 Plan Your Next Bake with S.D TIMERHydration is total water divided by total flour, counting every flour and water source in the dough — including the starter's own contribution. It sets crumb openness, handling difficulty, and a small but real shift in fermentation speed. Match your target hydration to the bread type you're making, account for how your specific flour absorbs water, and move in small increments when you're pushing into wetter territory. The percentage is a starting point for judgment, not a substitute for it.