Levain calculator

Build exactly the levain your recipe needs, at any hydration, from the starter you keep.

The levain you need

g

Add 10 to 20 g for what sticks to the jar.

%
%

As % of the fresh flour. 20% is a 1:5 build.

%

Levain or starter: what is the difference?

Your starter is the culture you keep and feed indefinitely. A levain is a one-off build made from a little of that starter, sized and hydrated for a specific recipe, and used up entirely in the dough. Building a levain lets you keep a small starter while baking big batches, or switch to a stiff or liquid levain without changing how you maintain your starter.

Worked example. A recipe calls for 220 g of 100% levain. With a 20% seed of a 100% starter, mix 20 g starter, 100 g flour and 100 g water.

For a stiff 50% levain of 165 g from the same starter: 20 g starter, 100 g flour and 45 g water. The starter brings 10 g of water with it, so (45 + 10) ÷ (100 + 10) = 50%.

The formula

Simple "1:5:5" builds ignore the fact that the seed brings its own flour and water. That is fine for 100% levains from 100% starters, but it drifts when the two hydrations differ. This calculator solves for the exact mix:

a = seed % ÷ (1 + starter hydration)
Fresh flour = levain ÷ ((1 + a) × (1 + levain hydration))
Starter = fresh flour × seed %
Fresh water = levain hydration × fresh flour × (1 + a) − water in starter

Tips

  • A larger seed percentage makes the levain ready sooner; a smaller one slows it down. Use that to fit the build into your day.
  • Use the levain near its peak, when it has risen well and is domed. The schedule planner helps you time it.
  • Plug the levain into the recipe calculator as the "starter", with the levain's hydration.

Limits of this calculator

  • It does not predict timing. Temperature, flour and seed amount all change how fast a levain ripens.
  • If the seed holds more water than the target hydration allows (a very stiff levain from a liquid starter with a large seed), it will ask you to change the inputs.