Sourdough Hydration Calculator

Hydration, properly counted

Hydration is total water ÷ total flour × 100 — and "total" means including the starter. A recipe of 500 g flour, 350 g water and 100 g starter at 100% hydration is not 70% hydration: total flour is 550 g and total water is 400 g, so true hydration is 72.7%. The calculator does this split for you: starter flour = starter ÷ (1 + starter hydration ÷ 100), starter water = the rest. If your starter is stiffer than 100% hydration — say 50% — it contributes proportionally less water, and the water to add rises to compensate.

A worked example

Take 500 g of bread flour at 70% hydration with 100 g of starter at 100% hydration and 2% salt. The starter holds 50 g flour and 50 g water, so total flour is 550 g and total water must be 385 g — meaning you add 335 g of water, not 350 g. Salt at 2% of total flour is 11 g, and the finished dough weighs 946 g. That 15 g water difference is small on paper but visible in the bowl: it is the gap between a dough that holds its shape and one that spreads.

Choosing your hydration

White bread flour at 65–70% suits most home bakers and most ovens. Adding whole wheat or rye raises absorption — a 50/50 white/whole wheat blend usually wants 72–75%. Enriched doughs with butter, milk or eggs behave differently again: the fat shortens gluten, so the same hydration feels softer. And remember hydration is not the only variable: flour protein, autolyse time, fermentation temperature and shaping all move the result. Use the calculator to remove the arithmetic, then judge the dough by feel — the numbers get you close, your hands finish the job.