Start from your loaf size — or the flour or starter you have — and get exact grams, true hydration that counts the starter, and a feed-to-bake plan for your kitchen.
Updated · How we source our numbers
Many sourdough recipes use 15–25% starter by flour weight. Count the starter’s own flour and water: a recipe printed at 72.5% hydration with 20% of a 100%-hydration starter is really 75%.
Sourdough recipes are written in baker’s percentages, but your starter complicates them: it is itself flour and water. This calculator treats the starter properly. You set the true hydration you want — all the water divided by all the flour, starter included — and it works backwards to the flour and water you actually add.
total flour = added flour + starter flour · added water = hydration × total flour − starter water
Salt is a percentage of the total flour, and the four weights always add up exactly to your dough weight. Set the starter to 0% and it works as an ordinary bread dough calculator.
Most recipes print hydration as added water over added flour. With 20% of a 100%-hydration starter, a recipe printed at 72.5% is really 75% — enough to change how the dough handles. The calculator shows both numbers so you can compare it with any recipe. See the sourdough hydration chart for the conversion at common starter amounts.
Switch Start from to the flour or starter in your kitchen and the recipe is built around it. Fill in Plan your bake and you get a timetable worked backwards from bake time: feed the starter, mix when it peaks, bulk, shape and proof. The starter’s peak window comes from the feeding ratio chart; your kitchen temperature decides whether to plan on its fast or slow end. Bulk and proof times are yours to enter, because they depend on your recipe and dough temperature.
Planning a whole weekend bake with a cold proof and a preheat? The bake planner builds the full dated timeline and adds every step to your calendar.
The result tells you how much starter the dough needs. Use the link under the recipe to open the sourdough starter calculator already set to that amount; it works out the feed and discard.