How to use the levain calculator
- Enter how much levain your recipe calls for – for example 100 g or 150 g.
- Add a small buffer so you still have enough after scraping the jar.
- Choose a seed ratio. This is how much fresh flour each gram of your starter gets. It sets how long the levain takes to peak.
- Set the levain's hydration. The calculator accounts for the flour and water already in your seed starter, so the finished levain hits your target exactly.
What is a levain?
A levain (also called a leaven or pre-ferment) is a portion of starter built specifically for one bake. Instead of using your whole starter jar, you take a small amount as a "seed", feed it the exact flour and water your recipe needs, and let it ripen. When it peaks, all of it goes into the dough.
Building a levain has three advantages: you don't need to keep a big starter, you can time the peak to fit your schedule, and you can shape its flavor – stiff levains taste milder, liquid levains tangier.
How the math works
The tricky part is that your seed starter already contains flour and water. If you want a 100% levain and your seed is a 100% starter, the math is easy. But if your starter is stiff (say 50%) and you want a liquid levain (125%), the water you add has to make up the difference. The calculator solves this for you:
Levain timing
At about 24 °C / 75 °F, a levain built at 1:2 (seed to flour) usually peaks in 6–8 hours; 1:5 takes around 9–12. Build it the night before with a larger ratio for a morning mix, or in the morning with a small ratio to mix in the afternoon. The schedule planner lays out the whole day.
Frequently asked questions
What's the difference between a starter and a levain?
A starter is the culture you keep and feed indefinitely. A levain is an off-shoot built from it for one specific bake, sized and timed for that recipe. Using a levain protects your main starter and lets you control timing.
Why add a buffer?
Some levain always sticks to the jar and spatula. A 10–15% buffer means you still have the full amount the recipe asks for.
What levain hydration should I use?
100% is the most common and easiest to mix. A stiff levain (50–65%) ferments more slowly and gives a milder, less acidic flavor; a liquid levain (125%+) ferments faster and tends to taste tangier.