Dough Hydration & Sourdough Starter
True dough hydration with a sourdough starter split into its flour and water, the salt percentage and prefermented share, or the water to add for a target.
The starter split into flour and water at its own hydration, total flour and water, the overall hydration against the added-only figure, salt as a percentage of flour, the prefermented share and total dough — or the water for a target.
Example: 500 g flour, 350 g water and 100 g of 100 % starter: the starter adds 50 g of each, so 400 over 550 is 72.7 % hydration — not the 70 % you get by ignoring it; salt 10 g is 1.82 %.
The starter
counts.
What hydration means, why the starter must be split before it is counted, how the target mode finds the water, and what the salt and prefermented figures tell you.
Hydration
Hydration is water over flour by weight. A starter is flour and water already mixed, so at 100 % hydration it is half of each, and at 80 % it is 1 part water to 1.25 flour: starter flour = starter ÷ (1 + h) and the rest is water. Add those to the flour and water you weigh out and the true hydration is total water over total flour — usually a little different from the added-only figure, and the difference grows with the amount of starter.
Target mode
Reverse the arithmetic and a target hydration gives the water to add: target × total flour less the water the starter already brings. If the starter alone exceeds the target, no water can be added and the page says so.
Salt and prefermented flour
Salt is shown as a percentage of the total flour, the baker’s-percentage convention. The prefermented share — the starter’s flour as a share of all flour — is what bakers vary to change flavour and fermentation speed.
What the number does not settle
Different flours absorb different amounts of water, so the same hydration handles differently; fermentation time and temperature are the recipe’s. Inputs stay in your browser; the same anonymous usage counts as the rest of the site apply.