Sourdough Starter Calculator
Tell it how much active starter your recipe needs and how you like to feed — it tells you exactly what to mix, and roughly when it'll peak.
The margin is extra so you're never scraping the jar — it becomes the seed for your next feeding. Peak times assume a healthy starter around 24 °C / 75 °F; colder kitchens are slower.
How feeding ratios work
A ratio of 1 : 2 : 2 means one part existing starter, two parts fresh flour, two parts water — by weight. Bigger feedings (1:5:5, 1:10:10) dilute the starter more, so it takes longer to peak but stays at its peak longer and tastes milder. Small feedings (1:1:1) peak fast and turn sour quickly.
| Ratio | ≈ Time to peak (24 °C) | Good for |
|---|---|---|
| 1:1:1 | 3–5 h | Quick same-day boosts |
| 1:2:2 | 4–6 h | Standard daily feeding |
| 1:3:3 | 5–8 h | Feeding in the morning, baking at night |
| 1:5:5 | 8–12 h | Overnight levain builds |
| 1:10:10 | 10–14 h | Mild flavour, long overnight builds |
Rule of thumb: your starter is ready when it has roughly doubled, smells pleasantly tangy, and a spoonful floats in water. If it's collapsing back down, it's past peak — still usable, but your bread will be more sour and slightly less lofty.