Hydration is the ratio of water to flour in your dough, expressed as a percentage. A dough with 500 g flour and 375 g water is 75% hydration. That single number tells an experienced baker more about your loaf than almost anything else.
At 60–65%, you have a stiff, bagel-like dough. Easy to handle, tight crumb, thick crust. Good for beginners and for shaping into precise forms like batards or sandwich loaves.
At 70–75%, you land in classic country loaf territory. Open but even crumb, crackly crust, forgiving to shape. This is where we bake most of our farmstand sourdough.
At 80–85%, the dough becomes slack and sticky. Handled well, it produces the wide-open, glossy crumb people chase on Instagram. Handled poorly, it pancakes. Bench flour, wet hands, and confident folds are the difference.
At 90%+, you're in ciabatta and focaccia territory. Almost pourable dough, huge irregular holes, chewy interior. Not better or worse than lower hydration — just a different bread.
Print the chart, tape it inside your flour cabinet, and start logging what you bake. Two months of notes will teach you more than any recipe.