Sourdough Levain Calculator

A levain is a pre-ferment built fresh for each bake from a small portion of your main starter. The word levain is French for leavening agent; it describes the same thing as a pre-ferment, young starter, or stiff starter build. The key distinction is that a levain is sized for a specific recipe, timed to peak at the moment you mix dough, and used in full — nothing is saved back.

Building a levain separately from your main starter gives you several practical advantages. It lets you adjust hydration independently of your main starter (a 65% hydration levain in a recipe that normally uses 100% hydration starter, for example). It lets you use a different flour blend — adding rye to the levain to accelerate fermentation without changing your starter's character. And it keeps your maintenance routine unaffected: you can feed your starter as normal and take a small amount off to build the levain at whatever time your bake schedule requires.

Levain percentage is the weight of your levain expressed as a percentage of your total flour weight. At 20%, a dough made with 800g flour uses 160g of levain. Higher percentages increase the amount of active yeast and bacteria entering the dough, which accelerates fermentation. Lower percentages slow it down.

The right percentage depends on your bake schedule, flour type, and kitchen temperature. For a same-day bake, 20% levain gives roughly 4.5–6 hours of bulk at 75°F / 24°C in our bulk model. For an overnight cold proof, drop to 8–12% to keep the dough from over-fermenting in the fridge. Whole wheat and rye doughs usually ferment faster, thanks to the extra nutrients and enzymes in those flours, so many bakers use a little less levain than for an all-white loaf.

8–12% → slow, overnight cold proof (long, complex flavour)

15–20% → standard country loaf at room temperature

20–25% → baguette, focaccia, same-day bake

25–30% → fast bake in cool kitchen or beginner schedule

Levain hydration can differ from your main starter's hydration and from your overall dough hydration. Most country loaf recipes call for a 100% hydration levain because it is easy to mix and incorporates easily into a wet dough. Stiff levains (50–65% hydration) usually peak more slowly and are used in pain de campagne and some rye breads. They change the flavour too, but the research I have read does not settle which way, so I treat that as something to taste for.

Flour blend changes fermentation speed. Rye or wholemeal in the levain flour usually brings the peak forward, because those flours carry more nutrients and enzymes than white flour. How much sooner varies with the flour and the starter, so I do not put a percentage on it. Use some rye in the levain if your kitchen runs cold or you want an earlier peak without increasing the seed, and check early the first time.

Timing is everything with a levain. The goal is to have it peak at about the moment you want to mix your final dough. Peak here means the highest point it rises to in the jar; it is a practical cue for when the levain is ready, not a measure of when the yeast is most active.

The simplest approach is to build the levain the day before a morning bake. With the 10% seed build in this calculator, I plan on 14–18 hours at 68°F / 20°C, so build it in the afternoon. For a bedtime build and a 7–8am mix, a 1:2:2 levain fits better (8–12 hours at 68°F). In a warmer kitchen (79–82°F / 26–28°C), use a bigger feed or a cooler spot to stretch the timing. If you need the levain to peak sooner, use more seed, add wholegrain flour, or move the jar somewhere warmer. The peak card above gives the estimate at three temperatures.

A levain at peak has stopped rising and sits at its highest point, often around double or more, with a domed top covered in bubbles and a clean, yeasty, mildly tangy smell. It should feel airy when you drag a spoon through it: light and slightly foamy, not dense or heavy.

The most reliable method is to mark the container right after building with a rubber band or tape. Doubling often comes first; peak is when the rise stalls and the dome is at its highest. Do not rely on timing alone. Temperature changes in your kitchen can move the actual peak hours away from the estimate.

Levain is slow or overactive

If your levain is not rising as expected, check the temperature first. A cool kitchen slows it noticeably, and in a cool room a slow 1:5:5-style build can take most of a day. Move the jar somewhere warmer or use more seed. If it rises and falls well before you need it, it is moving too fast for your schedule: use less seed or a bigger feed, find a cooler spot, or try a stiffer levain.

Check the parent starter

Poor starter health is another cause. If your main starter does not rise reliably within the usual window for its ratio (for a 1:1:1 feed I plan on 4–6 hours at 75°F / 24°C), it may not be active enough to drive a good levain build. Feed it twice daily for two or three days before your bake. A little whole wheat or rye in its feeds can also help a sluggish culture recover.

The levain is the anchor of your sourdough schedule. Everything else (autolyse, bulk fermentation, shaping, cold proof and baking) follows from when the levain peaks. Work backwards: set your target baking time, subtract your cold proof (8–16 hours), subtract shaping and pre-shaping (1 hour), subtract bulk fermentation (with 20% levain at 75°F / 24°C our bulk model estimates 4.5–6 hours; the bulk calculator adjusts it for your dough), subtract autolyse (30–60 minutes), and that gives you when the levain needs to be ready. Then count back by the expected peak time to find when to build.

For less experienced bakers, a simple schedule is: build a 1:2:2 levain at 9pm in a cool room, mix the dough at 7am, bulk until early afternoon, shape and cold proof, then bake the next morning. This spreads the work across two days with no early starts. The calculator's own 10% seed build is slower, so start it in the afternoon instead, and use the peak card to choose a cooler or warmer spot.