How to convert any yeast bread recipe to sourdough

Drop the packet of instant or active-dry yeast entirely. In its place, add ripe, active starter at roughly 20% of the recipe's total flour weight, a good default. So a recipe with 500g flour gets about 100g of starter. More starter means a faster (and slightly tangier) rise; less means slower. You can tune it later, but 20% is a reliable starting point that works for most loaves.

The starter you just added brought its own flour and water, so subtract those from the recipe or the dough will be too wet. A 100%-hydration starter is half flour, half water by weight: 100g of starter = 50g flour + 50g water. So reduce the recipe's flour by 50g and its water by 50g. Skip this step and you've effectively added 100g of extra liquid-and-flour the recipe wasn't written for, which is a common reason a first conversion comes out slack.

This is the biggest mental shift. Commercial yeast raises dough in 1 to 2 hours; a starter takes 4 to 12 depending on its strength and your kitchen temperature. So wherever the original recipe says "let rise 1 hour", read it as "let rise until roughly doubled", which will take much longer. Ferment to the dough's state, not the recipe's clock. Many bakers also move the final proof to the fridge overnight, which fits sourdough's slower pace and deepens the flavour.

Your first conversion is an experiment, and experiments are only useful if you record them. Note the starter percentage you used, how long each rise actually took, and how the loaf turned out. The second bake of the same recipe is where conversion really pays off, you adjust one variable from a known baseline instead of starting from scratch. Sourdough Tracker keeps that bake-to-bake thread so a converted recipe gets reliably better instead of being a fresh gamble each time.