Young and sweet
before peak
- Risen well, dome still rounded and climbing
- Sweet, overripe-fruit smell with little sourness1
- Chad Robertson prefers a young leaven like this for a milder loaf1
Sourdough starter timer · Feed planner
Tell it how you feed and how warm it is. It shows when your starter should peak — or works backward from when you need it ripe — and learns your starter’s pace from one logged feed.
Likely peak
5h 30m–9h 55m
after a 1 : 2 : 2 feed at 74°F
Flour changes the pace, but there’s no reliable published multiplier — so the clock learns it from feeds you log with this flour.
Every starter has its own pace. Log one feed and the range narrows to yours.
Log a feed ↓Enter how much ripe starter your recipe calls for.
Building a levain for a formula? The Baker’s Bench works out the levain for any recipe.
Middle of the published range — your starter may run faster or slower. Tap a cell to use it.
| Feed | 66°F | 70°F | 74°F | 78°F | 82°F |
|---|---|---|---|---|---|
| 1:1:1 | |||||
| 1:2:2 | |||||
| 1:3:3 | |||||
| 1:4:4 | |||||
| 1:5:5 | |||||
| 1:10:10 |
The estimate tells you when to look. These tell you what you’re looking at.
before peak
the estimate on the dial
past peak
About the float test: Floating isn’t proof. In King Arthur’s test, a starter floated at four hours while it was still two to four hours from ready. King Arthur float-test experiment (2019)
Note when it actually peaked. The clock takes the middle of your logged feeds and scales every estimate to your starter. Saved on this device only.
Set the ratio, flour and temperature above to match that feed first.
How the clock works
It depends mostly on two things: how much you dilute it when you feed, and how warm it is. In King Arthur’s 2025 feeding-ratio trial at 78°F, a 1:2:2 feed peaked at about 8 hours and a 1:4:4 feed at about 12. Bigger feeds take longer, though not in proportion to their size. For temperature, the clock assumes each drop of about 18°F (10°C) roughly doubles the time — a standard approximation; published rules of thumb vary a little. The Starter Clock uses a curve fitted to that trial and a temperature rule of thumb.
Home starters vary a lot. In published recipes from The Perfect Loaf and ChainBaker, starters were called ready after about 0.52 to 0.84 times King Arthur’s hours (the clock’s uncalibrated range starts at 0.55×) — “ready” rather than a measured peak, but a clear sign that home starters often run faster. That’s why the clock shows a range until you log a feed: one real observation of your own starter replaces the range with its actual pace, and it keeps learning as you log more.
Want ripe levain at 8am? Choose “Ready by a time” and enter when you’ll mix. The clock suggests when to feed and the ratio that should peak then — a small feed for a short gap, a big one (1:5:5, 1:10:10) to stretch overnight. The feed builder then turns the ratio into grams for the amount your recipe needs; the Baker’s Bench works out that amount for any formula.
The clock stops speeding up above about 84°F. In lab studies of sourdough microbes, the yeast grew fastest around 80°F while the bacteria peaked nearer 90°F — so warmer isn’t reliably faster, and the clock doesn’t pretend it is. Flour type and starter hydration change the pace too, but there’s no reliable published multiplier for them, so instead of guessing, the clock tunes itself to feeds you log with that flour. A starter straight from the fridge can take two or three feeds — a day or two — to get back to full speed (The Perfect Loaf). And the jar always outranks the estimate: look for the dome, the bubbles and the smell described above. King Arthur found a floating starter can still be hours from ready.
For day-to-day care, see the feeding guide; for a full bake, start with the beginner sourdough recipe.