How sourdough hydration calculator works
Hydration is a bakers'-percentage number: total water divided by total flour, written as a percentage. A dough at 70% hydration carries 700 g of water for every 1,000 g of flour. It is the single number that best predicts how a dough will handle — stiffer doughs around 60–65% are easy to shape, while wetter ones from 75–85% give an open, glossy crumb but demand confidence with sticky dough.
Your starter counts toward both totals, which is the step most home bakers miss. A starter fed at 100% hydration is exactly half flour and half water, so 100 g of it contributes 50 g of flour and 50 g of water. A stiffer starter at 50% contributes two-thirds flour and one-third water. The calculator splits whatever starter amount you enter using its own hydration and adds both parts to the totals.
Enter flour and water in grams, plus your starter amount and its hydration, and the result shows total flour, total water, overall hydration and final dough weight. Add a target hydration and it also solves backwards: for a goal of, say, 78%, it tells you the exact water to add (or remove) to hit that target with the starter you are using.