Sourdough Hydration Calculator
Calculate the true hydration percentage of any sourdough recipe, accounting for starter hydration.
Sourdough recipes list a starter amount without telling you what the hydration actually is once you account for the water and flour already in the starter. I built this calculator after spending too long calculating starter flour and water contributions by hand every time I tweaked a recipe.
A 100% hydration starter (equal parts flour and water by weight) contributes equal flour and water to your dough. 50g of starter = 25g flour + 25g water. Always account for starter when calculating true dough hydration.
What hydration means in bread baking
Hydration is the ratio of water to flour in a dough, expressed as a percentage. A 70% hydration dough has 70g of water for every 100g of flour. Higher hydration doughs are wetter, stickier, and produce more open, chewy crumbs, but are harder to handle. Lower hydration doughs are firmer, easier to shape, and produce tighter crumbs. Sourdough hydration typically ranges from 65% (fairly stiff) to 85%+ (very slack, for open-crumb loaves).
Why starter hydration matters
A sourdough starter contributes both flour and water to the dough. A 100g portion of a 100% hydration starter adds 50g flour and 50g water. If your recipe lists 500g flour and 350g water plus 100g starter (100% hydration), the true hydration is (350+50)/(500+50) = 400/550 = 72.7%, not the 70% you might calculate from just the listed flour and water.
Baker's percentages
Professional bakers use "baker's percentages" where every ingredient is expressed as a percentage of total flour weight. Flour is always 100%. Water at 70% means 70g water per 100g flour. Salt at 2% means 2g salt per 100g flour. This system makes scaling recipes trivial and allows direct comparison of recipes regardless of batch size. Hydration is the most important baker's percentage in sourdough.
Target hydration by bread type
65–70%: Rustic loaves, sandwich bread, baguettes. Firm, easy to shape, tighter crumb. Good starting point for beginners. 70–75%: Country loaves, standard sourdough. Moderate challenge, good oven spring, open crumb. 75–80%: Open-crumb sourdough, ciabatta. Sticky dough requiring good technique. 80%+: Very open crumb, requires confident handling. Better suited for experienced bakers.
Frequently asked questions
What hydration is my starter?
Most home bakers maintain a 100% hydration starter, equal weights of flour and water in each feeding. A thick starter (stiff levain) might be 50–80%. A liquid starter might be 125–150%. If you feed by volume rather than weight, your actual hydration varies, feeding by weight gives you a known hydration.
How do I adjust hydration mid-recipe?
Hold back 10–15% of the recipe water during mixing. After the flour is fully hydrated (autolyse), assess the dough feel. If it's too stiff, incorporate more reserved water. This technique (bassinage) lets you adjust for flour variation without committing to the full water amount upfront.
Why does hydration feel different even at the same percentage?
Different flours absorb water differently. Whole wheat and high-protein bread flour absorb more water than all-purpose. Freshly milled flour absorbs more than aged flour. Temperature, humidity, and mixing method all affect apparent dough consistency at the same hydration. Hydration is a starting point, adjust based on how the dough actually feels.