What is a levain and how is it different from starter?

A sourdough starter is the culture you maintain and feed regularly. A levain (or leaven) is a separate pre-ferment you build specifically for one bake — taking a small amount of your starter (the seed) and mixing it with fresh flour and water. The levain ripens for several hours, then gets incorporated into your dough. This separates your master starter from the baking process.

What is the seed percentage?

Seed percentage is the weight of existing starter you use, expressed as a percentage of the total flour in the levain. A 20% seed with 100g flour means you use 20g of starter. Lower seed percentages (10-20%) give a slower, more acidic fermentation. Higher seed percentages (25-50%) produce a faster, milder levain.

What hydration should I use for my levain?

Most sourdough recipes call for a 100% hydration (equal flour and water) levain because it is easy to mix and ripens predictably. Stiff levains (50-80% hydration) are used for baguettes and some sourdough styles to reduce acidity and improve extensibility. Liquid levains above 100% are used for very open crumb loaves.

What does a 1:5:5 build ratio mean?

A build ratio like 1:5:5 means 1 part starter to 5 parts flour to 5 parts water, all by weight. So with 10g starter you would use 50g flour and 50g water for 110g total levain at 100% hydration. Ratios with more flour and water (e.g. 1:10:10) produce a milder levain that peaks more slowly.

Does the starter hydration affect the calculation?

This calculator assumes your existing starter is 100% hydration (equal flour and water by weight), which is the most common maintenance hydration. If your starter is stiffer or more liquid, the actual flour and water contribution from the seed differs slightly, but for most recipes the difference is negligible for home bakers.

How much levain do I need for a loaf?

A typical country loaf uses 15-20% levain as a percentage of total flour weight. If your recipe calls for 500g flour, you would want roughly 75-100g of levain. Build slightly more than needed and discard the remainder — this accounts for any residue left in the jar.

Levain Build Calculator

Name: Levain Build Calculator
Availability: InStock
Author: Nham Vu

Enter your target levain weight, hydration percentage, and seed percentage to get the exact amounts of starter, fresh flour, and water needed.

Quick Presets

Build Parameters

Target Levain Weight (g)

Total amount of levain you want to build.

Hydration (%) 100%

% Liquid

100% = equal flour and water by weight.

Seed (%) 20%

% Moderate

Starter as % of total levain flour.

Levain Build

Starter (Seed)

Existing active starter

—

grams

Fresh Flour

Bread flour or as specified

—

grams

Water

Room temperature or as specified

—

grams

Total Levain

—

grams

Build Ratio

—

Starter : Flour : Water

Composition

Flour share

Water share

Starter share

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Summary

Enter your target levain weight, hydration percentage, and seed percentage to get the exact amounts of starter, fresh flour, and water needed.

How it works

Enter your target levain weight in grams (the total amount of levain you want to build).
Set the hydration percentage — 100% means equal flour and water by weight; 80% means 80g water per 100g flour.
Set the seed percentage — this is the amount of existing starter expressed as a percentage of the total flour in the levain.
The calculator instantly shows the grams of starter, fresh flour, and water needed.
The build ratio (starter : flour : water) updates automatically and can be copied to your notes.
Use presets for common levain styles or adjust all three inputs freely.

Use cases

Plan a same-day levain build for a baguette or country loaf.
Scale a stiff levain (60-80% hydration) for whole-wheat or rye breads.
Build a liquid levain (100-125% hydration) for open-crumb sourdough.
Quickly check a recipe build ratio before committing to a large batch.
Calculate starter quantities when preparing multiple levain jars at once.
Adapt a recipe build ratio to a different target levain weight.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu