“Ready” means your starter is at its peak — the moment it's most active and has the most gas to leaven your bread. Catch it too early and your dough rises sluggishly; too late and it's already declining. Here's how to recognise that window, and why the test everyone reaches for first is the one to trust least.
What a ripe starter looks like
A ready starter has roughly doubled from where it was after feeding, is domed slightly on top (like a hill, not a crater), and is just about to start falling. That peak is the target. The signs that tell you you're there:
- It doubled. Mark the jar right after feeding; when it reaches twice that line, it's at or near peak. This is the single most reliable sign — track it every time.
- It's domed. At peak the surface curves gently upward. A flat or sunken surface means it's past peak and starting to deflate.
- It's bubbly throughout. A network of bubbles through the body and along the sides of the jar, not just a few on top.
- It smells tangy and yeasty. Like mild yogurt or beer. A sharp nail-polish (acetone) smell means it's hungry and over-acidic — feed it.
The float test — and why it's the least reliable sign
The float test — dropping a spoonful into water to see if it floats — is the famous one, but it's also the one to trust least. It checks gas content, which is only loosely tied to peak: a starter can float when it's already past peak (residual gas) or sink when it's at peak but dense. And a rye or whole-grain starter may never float at all, because those flours trap gas less well.
The sign beginners skip: consistency
Here's the one most guides rush past. A single good rise doesn't prove a starter is ready to leaven bread — it might have caught a warm spot or got lucky. What proves it is doubling consistently across about three feedings in a row, peaking on a predictable timeline. A newly-made starter usually needs 10–14 days of regular feeding before it's that reliable. Repeatability is what experienced bakers trust most, and what beginners check least.
Timing your bake around the peak
Once you know how long your starter takes to peak at a given ratio and temperature, you can time the last feeding so it peaks exactly when you want to mix dough. At a warm room temperature a 1:1:1 feed peaks in about 4–6 hours, a 1:5:5 in 8–12 — the feeding calculator shows the peak window for any ratio so you can plan backwards from your bake.
Sources and method: see our methodology and references.