One of the fundamental properties of a dough. It refers to the ratio of water to flour used in the recipe. The measurement of that ratio is usually in terms of baker's percentage (which quantifies all ingredients as a percentage of the total amount of flour used). Most breads are hydrated between 60% and 80%, with some exceptions going higher or lower.

Usually breads with a higher hydration have more open crumbs, that is because hydration is essential to gluten development, which directly influences the dough structure. On the other hand, breads made with lower hydration are usually denser. These effects can be balanced by using different techniques (such as folding) or adding ingredients to the dough.