Convert a yeast recipe to sourdough

Swap the yeast in any bread recipe for sourdough starter, with the flour and water adjusted so the dough stays the same.

The yeast recipe

g

Add up every flour in the recipe.

g

Or milk; 1 ml of water weighs 1 g.

Your starter

%

Of the flour. 20% is a common starting point.

%

How the conversion works

Commercial yeast adds almost no weight to a dough, so you can't simply replace it gram for gram. Sourdough starter is different: it is made of flour and water. If you add 100 g of starter on top of the original recipe, you add 50 g of extra flour and 50 g of extra water, and the dough is no longer the recipe you started with.

This converter takes the starter's flour and water out of the recipe's own flour and water. The total flour, total water and therefore the hydration stay exactly as the original. Salt and every other ingredient stay the same; only the yeast is left out.

Worked example. A recipe with 500 g flour, 350 g water, 10 g salt and 7 g instant yeast is a 70% hydration dough.

At 20% starter (100% hydration), you need 100 g of starter, which holds 50 g flour and 50 g water. Weigh out 450 g flour, 300 g water, 100 g starter and 10 g salt, and leave out the yeast. The dough is still 70% hydration.

The formula

Starter = recipe flour × starter %
Flour to use = recipe flour − flour in starter
Water to use = recipe water − water in starter

What changes when you switch to sourdough

  • Time. A starter raises dough more slowly than commercial yeast, so expect bulk fermentation and proofing to take noticeably longer. Go by how the dough looks and feels rather than the original recipe's timings. The schedule planner helps you fit the longer steps into your day.
  • Flavour. The bread will taste tangier, more so with longer, cooler fermentation.
  • Enriched doughs. Recipes heavy in sugar, butter, eggs or milk (brioche, cinnamon rolls) ferment more slowly again with a starter. Many bakers raise the starter percentage for these.
  • Starter strength. Use your starter when it is active and near its peak. A sluggish starter is the most common reason a converted recipe fails to rise.

Limits of this converter

  • It adjusts flour and water only. If the main liquid is milk, the result is still right by weight, but milk adds fat and sugar that slow fermentation.
  • If the recipe has very little liquid and you choose a lot of liquid starter, the starter would bring more water than the recipe contains; the converter will ask you to use less starter or a stiffer one.