FlourScaleWhat sourdough hydration means
Hydration is the weight of water in a dough divided by the weight of flour, expressed as a percentage. A dough with 1,000 g flour and 750 g water is 75% hydration. It is the single biggest factor in how a dough feels: around 65% is firm and easy to shape, 70–75% is the typical range for an open country loaf, and 80% or more is slack, sticky and best handled with wet hands and coil folds.
Sourdough adds a complication. Your starter is itself flour and water, so a recipe that lists "450 g flour, 325 g water, 100 g starter" is not 72% hydration. The starter brings extra flour and extra water into the dough, and ignoring it can put your numbers off by several points — enough to explain why a dough feels wetter than the recipe promised.
How the true hydration is calculated
The calculator splits the starter into its flour and water using its hydration. A 100% hydration starter (equal weights of flour and water) is half flour, half water. A 50% (stiff) starter is two-thirds flour and one-third water. In general:
- starter flour = starter weight ÷ (1 + starter hydration)
- starter water = starter weight − starter flour
- true hydration = (water + starter water) ÷ (flour + starter flour) × 100
The second box runs the formula in reverse. Enter the flour and starter you plan to use and a target hydration, and it returns exactly how much water to add — handy when you switch to a stiff starter or a different flour.
Worked example
450 g flour, 325 g water, 100 g starter at 100% hydration and 10 g salt.
- Starter flour = 100 ÷ 2 = 50 g; starter water = 50 g
- Total flour = 450 + 50 = 500 g; total water = 325 + 50 = 375 g
- True hydration = 375 ÷ 500 = 75% (not the 72% you get by ignoring the starter)
- Salt = 10 ÷ 500 = 2% of total flour
Choosing the right hydration
Different flours absorb different amounts of water. Whole wheat and freshly milled flours drink more, so a 75% whole wheat dough can feel stiffer than a 72% white dough. Lower-protein all-purpose flour gets sticky sooner than strong bread flour. If you are new to sourdough, start around 68–70% and raise hydration a couple of points at a time as your handling improves. Holding back 5–10% of the water and adding it during mixing ("bassinage") lets you judge the dough before committing.
Remember that additions change the feel too: seeds and grains soak up water, while oil and honey make a dough feel softer without adding water.