Sourdough Starter Peak Calculator
Estimate a broad starter peak window from feeding ratio, room condition and the starter's observed state, with visual readiness taking priority. Inputs stay in your browser.
The estimate uses King Arthur's warm-room ratio observations as a planning curve, then widens the window because every starter and kitchen behaves differently.
Context matters.
- A ripe starter is typically doubled or tripled, bubbly and just beginning to level or sag; visible behavior overrides the estimate.
- Higher feed ratios generally take longer to peak, while warmer conditions speed fermentation.
- If a starter has pink or orange growth, fuzzy mold or a clearly rotten smell, discard it rather than tasting or baking with it.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Estimate a broad starter peak window from feeding ratio, room condition and the starter's observed state, with visual readiness taking priority. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Starter fed on, Feeding time, Starter : flour : water ratio, Flour and water multiple and Room condition and 1 additional field supplied in the form.
- Apply the scope. It applies the Home sourdough fermentation estimate — observed starter condition overrides the clock reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
The estimate uses King Arthur's warm-room ratio observations as a planning curve, then widens the window because every starter and kitchen behaves differently.
- Estimated peak windowAug 23, 2026 at 11:45 – Aug 23, 2026 at 14:45
Calculation purpose: Estimate a broad starter peak window from feeding ratio, room condition and the starter's observed state, with visual readiness taking priority. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-22 · Next review due 2027-02-22. The source panel below contains the linked evidence.
What to know before using the result.
Does feeding ratio change starter peak time?
Generally, a larger feed relative to starter takes longer to peak under similar conditions, but starter strength and temperature create wide variation.
Is the calculated time more important than appearance?
No. A doubled, bubbly, domed starter or a starter already falling provides stronger evidence than a clock estimate.
What if the starter has pink or orange growth?
The calculator stops the timing result and advises discarding clearly spoiled starter rather than using a schedule to override a safety concern.