Sourdough starter feeding calculator
Calculate seed starter, flour, and water for a chosen total weight and feeding ratio.
How to use the result
Seed weight = target total ÷ (1 + flour parts + water parts). Multiply the seed by each ratio to find the additions. Ratios are by weight, not volume. The target total includes the seed starter.
Worked example
150 g total at 1:2:2 by weight = 30 g seed starter + 60 g flour + 60 g water.
Before changing the recipe
This portioning calculation does not predict readiness, fermentation time, or safety. Equal flour and water additions keep a 100%-hydration seed at 100%; they do not instantly turn a differently hydrated seed into a 100%-hydration starter. Allow enough total for your recipe and the starter you intend to retain.
Reference: King Arthur Baking: sourdough feeding ratios · Accessed October 6, 2026.
Calculation tool · Editorial review pending