Read the ratio in order
This tool uses seed starter : flour : water, all by weight. A 1:2:2 feed contains five total parts. To finish with 250 g, divide 250 by five: keep 50 g seed starter, add 100 g flour and 100 g water. The seed is included in the final weight.
Plan enough for the next bake
Decide how much ripe starter the recipe needs, then add the amount you want to keep. A recipe needing 200 g plus a 50 g reserve calls for a 250 g target. You can change that target without changing the feeding ratio. The result is a quantity plan, not a guarantee that the starter will peak on a specific schedule.
Hydration after feeding
Equal flour and water additions do not necessarily make a 100% hydration starter if the seed is unusually stiff or liquid. The final hydration includes the seed’s flour and water. With a 50% hydration seed, the same 1:2:2 feed finishes below 100% hydration.
When to use another tool
Use the sourdough hydration calculator to incorporate ripe starter into dough. Feeding ratios describe refreshments; baker’s percentages describe ingredients relative to flour. Keeping those two conventions separate prevents confusing a 1:2:2 feed with 200% dough hydration.
Questions, answered
Can this tell me when the starter will peak?
No. Temperature, flour, starter condition and feeding history affect the timing. Observe your starter rather than using a fixed prediction.
What if I want 1:5:5?
Enter 5 for flour parts and 5 for water parts. The target is divided into eleven parts, one of which is seed starter.