Sourdough Starter Calculator

Flour and water grams are each independently rounded to whole numbers before actual hydration is recalculated as (water grams / flour grams) * 100, so the rounding on two separate values compounds into a small drift from your original input. This is most noticeable on small batches — a 50 g total batch has less room to absorb rounding error than a 2,000 g one — and is expected behavior, not a bug in the ratio math.

Existing starter is calculated first as targetTotal times (inoculation / 100), and flour and water are then split only from whatever remains after that starter amount is subtracted. Because a higher inoculation percentage claims a bigger share of your fixed target total up front, less is left over to divide between fresh flour and water — the total weight fed stays the same, but the ratio of old-to-new material shifts.

Peak hours uses a tiered lookup on inoculation alone — 4 hours at 30% or above, 6 hours at 15–29%, and 8 hours below that — independent of hydration or total batch size. A larger proportion of already-active mature culture relative to fresh flour means there's more established yeast and bacteria working the new flour and water from the start, so it reaches peak rise measurably sooner than a thin, low-inoculation feed.

No — feedingSchedule only affects the peakHours output (multiplying the base estimate by 0.8 for twice-daily) and the feedsPerDay value; it plays no role in the starterGrams, flourGrams, or waterGrams calculations, which depend solely on targetTotal, hydration, and inoculation. Feeding twice a day changes how often and how quickly you feed the same ratio, not the ratio itself.