Calculator
Starter feeding and levain
Feed mode turns a seed:flour:water ratio and the grams you keep into flour and water to add. Levain mode splits a target weight backward and can download a calendar reminder. Peak times are estimates, and only the ratios King Arthur timed are filled in.
Quick answer. Keeping 20 g and feeding 1:1:1 adds 20 g flour and 20 g water. The jar then holds 60 g.
Grams
60 g after feeding · 100% water in the feed
| Seed to keep | 20 g |
|---|---|
| Flour | 20 g |
| Water | 20 g |
Hydration here is the water you add divided by the flour you add. It assumes the seed is already at that hydration.
A ratio is seed:flour:water by weight. Keeping 20 g at 1:2:2 adds 40 g flour and 40 g water, 100 g in the jar. King Arthur calls 1:1:1 the minimum useful feed. At about 78°F their 2025 trial found a healthy 1:1:1 usually peaks in about 4–6 hours, and can take 4–8; it had doubled by 4 hours and was beginning to fall at 8. A 1:4:4 feed before bed is ready roughly 12 hours later. They do not list a peak for 1:2:2 or for other ratios. The calendar file is one 15-minute event, counted backward from the use-at time, with floating local times and no time-zone suffix.
Questions
- How do I feed sourdough starter by ratio?
- A ratio is seed:flour:water by weight. Keep 20 g and feed 1:2:2 and you add 40 g flour and 40 g water. The seed is what you keep. The rest of the jar, if you are discarding, is not part of this calculation.
- What is a 1:1:1 starter feeding?
- Equal weights of seed, flour, and water. King Arthur calls that the minimum useful feed. Their 2025 trial, at about 78°F, found a healthy mature starter at 1:1:1 usually peaks in about 4–6 hours and can take 4–8. In that trial it had doubled by 4 hours and was beginning to fall at 8. The reminder starts at 4 hours so you can move it.
- How long until a 1:4:4 feeding peaks?
- King Arthur says a 1:4:4 feed before bed is ready roughly 12 hours later. The reminder uses 12 hours for that ratio. They do not publish a peak time for 1:2:2 or for other ratios on that page, so those reminders stay blank until you type your own hours. Peak times are estimates for a warm kitchen, not a measurement of your starter.
- How do I build a levain for a recipe?
- Enter the grams you need, the hydration, and how much new flour you want per part of seed. Water follows the hydration. The page splits the target weight backward into seed, flour, and water. It assumes the seed you keep is already at that same hydration.
- What does the calendar file contain?
- One event, “Feed levain”, starting the number of hours you chose before the use-at time, and lasting 15 minutes. Times are floating local times, with no time-zone suffix, the same way the bake planner writes a calendar. Change the hours before you download. The file does not know when your starter actually peaks.
Last reviewed 1 November 2026.
Sources
Peak times are only the 1:1:1 and 1:4:4 figures on that King Arthur page. The reminder starts at the early end of the 1:1:1 range (4 hours) or at their 12-hour note for 1:4:4, and you can edit it. No peak time is invented for any other ratio.