Baking formulas and oven work
Sourdough Starter Hydration Calculator
Calculate a starter’s hydration, flour content, and water content from its component weights or a known total.
Describe the maintained culture
Flour and water in the maintained build
Method basis: The hydration result describes the entered feed flour and water, while retained starter is shown only in build weight.
Hydration by weight
A 100% hydration starter contains equal flour and water by weight. It does not mean the mixture is entirely water or that water is 100% of total mass.
Retained starter already contains flour and water. For exact composition after repeated feeds, carry forward those components instead of treating the retained portion as an unknown third material.
Retained culture carries prior composition
Rye, whole-wheat, and white starters can look and ferment differently at an identical hydration because their absorption and microbial activity differ.
Equal flour and water
Example inputs are flour in starter of 100 g, water in starter of 100 g, retained ripe starter of 20 g. They produce starter hydration of 100.0% and new flour and water of 200.0 g. If the retained starter composition is uncertain, treat the result as the hydration of the new feed rather than the entire culture.
For the next starter step, use calculators that plan the next feed, prepare a separate levain and carry starter into final dough.
Culture behavior beyond hydration
Starter consistency is not a precise fermentation clock.
Feeding temperature and inoculation change ripening speed independently of hydration.
Flour choice changes the culture
A change in flour may deserve a new observation even when the percentage stays fixed.
A starter record that survives the next feed
Record feed weights, retained amount, flour blend, water temperature, room temperature, and the maturity cue used before refrigeration or mixing.
When precision matters, maintain a component ledger or refresh through enough known feeds that the old retained fraction becomes negligible. Calling the full build 100% hydration without knowing the retained starter can conceal a small but real difference.
Use visual rise, aroma, acidity, and structure with elapsed time. The percentage describes composition; it does not certify that a starter is ripe, balanced, or strong enough to raise dough.
If the culture is kept stiff for storage and converted to liquid for a recipe, make the transition through weighed feeds and label which build enters the final dough.
For a conversion between stiff and liquid maintenance, calculate the new feed rather than pouring water into an unknown quantity by eye. A weighed transition preserves traceability and makes the next maturity observation useful.
Starter-composition questions
Is a liquid starter always 100% hydration?
No. Liquid is a handling description; the actual percentage must come from flour and water weights.
Can cups be used?
Weight is preferable because equal volumes of flour and water are not equal masses.