Stiff Sourdough Starter (50% Hydration): How to Convert a Recipe

A stiff starter has half as much water as flour. Swapping one for a 100% hydration starter at the same weight changes your dough, so here's how to convert properly.

What "50% hydration" means for a starter

Starter hydration is water weight ÷ flour weight × 100, just like dough. A 50% starter has 50 g of water for every 100 g of flour, so it's a firm, kneadable ball rather than a batter. Italian lievito madre is a traditional stiff starter, usually kept somewhere around 45–50%.

To split any starter into flour and water: flour = starter weight ÷ (1 + hydration), with hydration as a decimal. The rest is water.

• 100 g of 100% starter = 50 g flour + 50 g water
• 100 g of 50% starter = 66.7 g flour + 33.3 g water

Turning a 100% starter into a 50% one

Take 20 g of your 100% starter (10 g flour + 10 g water) and feed it 50 g flour and 20 g water. Total: 60 g flour and 30 g water, which is 50% hydration. Knead it into a ball, then keep feeding at a flour-to-water ratio of 2:1 (for example 1 part starter : 2 parts flour : 1 part water by weight) and it stays at 50%. Give it a few feeds to settle into a predictable rhythm.

Swapping starters in a recipe without changing the dough

The cleanest method is to keep the same amount of flour inside the starter (the prefermented flour), then fix the water.

1. Work out the flour in the original starter: 100 g of 100% starter → 50 g flour.
2. Stiff starter needed: 50 × (1 + 0.5) = 75 g of 50% starter (50 g flour + 25 g water).
3. Water difference: the original starter brought 50 g water, the stiff one brings 25 g, so add 25 g more water to the dough.

If you simply swap 100 g of stiff starter in for 100 g of liquid starter and change nothing else, true hydration falls to (350 + 33.3) ÷ (450 + 66.7) = 74.2%. That's a noticeably stiffer dough.

Going the other way: 50% to 100%

A recipe calls for 100 g of stiff starter (66.7 g flour + 33.3 g water) but yours is 100%. Use 66.7 × 2 = 133 g of 100% starter (66.7 g flour + 66.7 g water) and remove 33 g of water from the dough. Total flour and water stay the same.

In the calculator

Set "Starter hydration" to 50 and the calculator counts the starter correctly. For example: total dough 900 g, water 70%, starter 20%, starter hydration 50%, salt 2% gives 469 g flour, 328 g water, 94 g starter and 9 g salt, with a true hydration of 67.6%. Note that the starter percentage stays a share of the flour you add, so a stiff starter at the same percentage brings more flour and less water than a liquid one. The starter percentage guide covers the conventions.

Practical differences

• Many bakers find a stiff starter ferments more slowly and stays usable for longer between feeds, especially at cooler temperatures.
• Flavour differences between stiff and liquid starters are often reported, but they depend on temperature, flour and timing as much as hydration.
• A stiff starter is harder to mix in. Breaking it into small pieces in the dough water first helps.
• To build a stiff levain for a bake, use the same ratio maths as in levain build ratios, with flour : water at 2:1.

FAQ

How do I convert a 100% hydration starter to 50%?

Feed a small amount of your starter with flour and water at roughly 2:1. For example, 20 g of 100% starter plus 50 g flour and 20 g water gives 60 g flour and 30 g water in total, which is 50% hydration.

How much stiff starter replaces 100 g of liquid starter?

To keep the same prefermented flour, use 75 g of 50% starter in place of 100 g of 100% starter, and add 25 g of extra water to the dough.

Does starter hydration change dough hydration?

Yes. At the same starter weight, a 50% starter adds more flour and less water than a 100% starter, so the dough's true hydration drops unless you add water.

Is a stiff starter the same as lievito madre?

Lievito madre is a traditional Italian stiff starter, usually kept at around 45–50% hydration. So it's one kind of stiff starter.