Sourdough Hydration Calculator

Total dough hydration is the ratio of all water to all flour in a recipe, expressed as a baker's percentage — but with sourdough, some of that flour and water is already locked up in your starter, which this calculator accounts for explicitly rather than treating hydration as a simple flour-plus-water split. It first finds how much flour and water the starter itself contributes: starter weight is your total flour times the starter percentage, and because a starter's own hydration can differ from your target dough hydration, the calculator backs out the starter's flour content as starterWeight / (1 + starterHydration/100) and the water as whatever's left. From there it subtracts the starter's flour and water contributions from the totals needed to hit your target hydration, leaving the additional flour and water you actually need to add at mixing. Salt is calculated separately as a flat percentage of total flour, added on top rather than counted toward hydration.

The "actual hydration" output re-derives the water-to-flour ratio from the final total water and total flour figures — but because total water is defined directly from your target hydration percentage, this number is mathematically identical to what you entered (aside from the final display rounding), so treat it as a confirmation that your target was applied correctly rather than an independent check that could reveal drift. Loaf count is a rough estimate assuming 500g dough balls, and bulk ferment time is a coarse tiered guess (4/6/8 hours) based only on starter percentage, ignoring temperature entirely — since the same starter percentage can ferment twice as fast at 80°F as it does at 65°F, watch your dough's actual rise rather than relying on the printed hour count. The most common mixup here is forgetting that starter hydration and target dough hydration are two separate numbers: a 100%-hydration starter added to a 65%-target dough still needs less added water than the naive total suggests, precisely because the calculator is crediting the starter's own water toward your target.