Sourdough Calculator

Works out how much starter, flour and water to use when feeding a sourdough starter or building a levain, and finds the true hydration of a sourdough recipe once the flour and water inside the levain are counted.

How to use

1. On "Feed the starter", pick a ratio such as 1 : 2 : 2 and enter the starter you need after feeding; the starter to keep, flour and water appear at once.
2. Enter "Starter you have now" to see how much to discard.
3. On "Build a levain", enter the levain your recipe needs and an extra percentage for what sticks to the jar.
4. On "Dough", choose "Check my recipe" to see the true hydration, or "Plan from targets" to get the levain, flour, water and salt for a target hydration.

How it works

• Flour in the levain = levain ÷ (1 + levain hydration). True hydration = (water + water in the levain) ÷ (flour + flour in the levain) × 100.
• The levain percentage is the levain weight as a percentage of total flour, including the flour inside the levain.
• Fermentation times are not calculated, because they depend on temperature and on how active the starter is.
• Inputs are saved only in this browser.

Questions and answers

What does a 1:2:2 starter feeding mean?

One part starter, two parts flour and two parts water by weight. For 100 g of fed starter that is 20 g starter, 40 g flour and 40 g water.

Does the levain count towards hydration?

Yes. 100 g of levain at 100% hydration adds 50 g of flour and 50 g of water. 450 g flour, 325 g water and that levain give 75% hydration, not 72%.

How much levain should I use?

There is no single amount; it depends on the recipe and on how fast you want the dough to rise. Enter your recipe's levain and the tool shows it as a percentage of total flour, which makes recipes easy to compare.

What is a stiff starter?

A starter with less water than flour, for example 50 to 60% hydration. Change "Starter hydration" and the water amount follows.