Understanding Sourdough Hydration: What the Percentages Mean

What Hydration Actually Measures

Hydration is the weight of water divided by the weight of flour, multiplied by 100, expressed as a baker's percentage. Mix 350g of water into 500g of flour and you have 70% hydration (350 / 500 = 0.70). Because it is a ratio, it stays constant whether you scale a recipe up to 1000g of flour or down to 250g, which is why bakers trade recipes in percentages instead of cups.

In the baker's percentage system, flour is always the 100% baseline and every other ingredient is measured against it. A standard loaf reads flour 100%, water 70%, salt 2%, starter 20%. That structure lets you compare two recipes at a glance and lets a tool like the hydration calculator convert a target percentage straight into gram weights for any batch size.

How Hydration Changes the Loaf

More water means a slacker, stickier dough that traps larger, more irregular gas pockets, producing the open crumb bakers photograph. Less water gives a firm, cohesive dough with a tight, even crumb that slices cleanly for sandwiches. The same flour and starter can make either bread; the water percentage is the main lever.

Hydration also drives handling and oven spring. Wetter dough flows and spreads, so it needs strong gluten and confident shaping to hold height, but when it works it springs dramatically because the extra steam inside expands the crumb. Drier dough holds its shape effortlessly and forgives clumsy handling, at the cost of a denser interior and a slightly tougher chew.

Low Hydration: 60-70%

Dough at 65% hydration is firm, dry to the touch, and shapes almost like modeling clay, which makes it the natural starting point. It bakes into a close, uniform crumb ideal for sandwich bread, bagels, and enriched doughs where butter and egg already loosen the structure. You can knead it conventionally on the bench without the dough sticking to everything.

If you are new to sourdough, start at 68-70%. That is wet enough to give a pleasant, slightly open crumb but dry enough to handle with plain floured hands and no special coil-fold technique. Master the full process at this level, then raise hydration in small steps once the fundamentals feel automatic.

Hydration only means anything if you weigh in grams. Measuring flour by the cup swings 20-30% between a packed and a spooned cup, which is enough to turn a stated 72% recipe into anything from 65% to 82% in practice. A scale with 1g resolution and a tare button is what makes the percentage real.

Medium Hydration: 70-78%

The sweet spot for everyday sourdough is 72-75%. This range delivers a genuinely open crumb while staying workable for anyone with a few loaves behind them, and it is where most bakery boules and country loaves live. The dough is tacky but does not flow off the bench.

At 75% the process, not the mixing, does the work. Build strength with three or four sets of stretch and folds spaced 30-45 minutes apart during a 4-6 hour bulk ferment, give a 20-30 minute bench rest after preshaping, and shape with intention to set surface tension. Wet hands and a bench knife keep the sticky dough moving without adding stray flour.

High Hydration: 78-90%

Doughs above 80% hydration give the dramatic, wildly open crumb with large glossy holes, but they behave like a thick batter and punish weak gluten. They demand excellent dough development, decisive handling, and a strong final shape or they spread flat on the peel. This is the deep end, not the place to start.

Ciabatta and some artisan loaves run 85-90%, and at that point traditional kneading is useless. Bakers switch to coil folds and lamination, stretching the dough into a thin sheet on a wet counter to align gluten without adding flour. A banneton and a well-preheated Dutch oven become close to mandatory to hold the shape until the crust sets.

Flour Absorption Changes the Number

Not all flours drink the same amount of water. Whole wheat and rye carry bran and germ that absorb far more than refined white flour, so a dough at 75% hydration with bread flour can feel like 80% with white flour but distinctly dry at 75% with 100% whole wheat. Whole grain flours often want an extra 5-10 percentage points of water to reach the same feel.

Protein content matters too. A strong bread flour near 12-13% protein forms more gluten and holds more water than an all-purpose flour at 10-11%, so it can carry higher hydration while staying manageable. Because absorption also drifts with the flour's freshness and how dry your kitchen is, always judge the dough by feel and adjust the last 20g of water rather than trusting the recipe number blindly.

Raising Hydration Step by Step

Do not jump from a comfortable 70% straight to 82%; move in 3-5 percentage point increments and bake at least twice at each level before climbing again. From 500g of flour, a 5-point rise means just 25g more water, small enough to adapt to but large enough to feel. Log the crumb, the stickiness, and the final height each time so you know exactly which level is your current ceiling.

Each rise usually calls for one more set of stretch and folds or a switch toward coil folds, plus wetter hands and a lighter touch at shaping. Support the higher-water dough with a longer cold retard in the fridge at 4 °C for 12-16 hours, which firms the dough and makes a slack 78-80% loaf far easier to score and load. When a level stops producing a clean, tall loaf, you have found the limit of your current flour and technique, and that is the number to master before pushing on.

Reading Too Wet vs Too Dry

A dough that is too wet slackens into a puddle, sticks stubbornly to everything, tears rather than stretches during folds, and bakes flat with a pale, gummy crumb. A dough that is too dry feels tight and resistant, fights back when you try to stretch it, shows a dense tight crumb, and often cracks at the surface during proofing. Both are fixable at the next bake by moving hydration 3-5 percentage points the other way.

Climate is the hidden variable. A humid summer kitchen leaves flour holding more ambient moisture, so the same recipe bakes wetter and you may drop water 2-3 percentage points; a dry winter room does the reverse. Change hydration in small, deliberate steps, note what each move does to crumb and handling, and within a handful of bakes you will read the dough by touch instead of the calculator.