Sourdough Starter Feeding Calculator
Feeding a sourdough starter is just weight arithmetic on a ratio. You keep a portion of the existing culture and add flour and water in proportion to it, written as starter : flour : water. This calculator takes the amount of starter you keep, your chosen flour and water parts, and the current hydration of your starter, then returns exactly how much flour and water to add, the total fed weight, and the final hydration of the refreshed starter. Use it to scale up before a bake, switch ratios, or move between liquid and stiff starters.
Feeding ratio formula
flour to add = kept starter * flour part
water to add = kept starter * water part
existing flour = kept / (1 + hyd/100)
existing water = kept - existing flour
final hydration % = (existing water + water added) / (existing flour + flour added) * 100
The parts are relative, so 1:5:5 and 50:250:250 give the same fed starter. Splitting the kept starter into its own flour and water by its hydration makes the final hydration exact.
Feeding notes
- A 1:1 flour to water feeding yields a 100 percent hydration liquid starter.
- Larger ratios such as 1:5:5 lengthen the time to peak and suit warm kitchens.
- Stiff starters use less water, for example 100 g flour to 50 g water (50 percent).
- Discard or bake with the starter you do not keep before feeding.
- Feeding cadence is a craft choice driven by temperature and routine.
Sourdough feeding: frequently asked questions
What does a feeding ratio mean?
A feeding ratio is written starter : flour : water, for example 1:5:5. It means for each part of existing starter by weight you add five parts flour and five parts water. A 1:1:1 feeding doubles the starter quickly; a 1:5:5 feeding gives a longer, cooler rise. The first number is the starter you keep.
How much flour and water do I add?
Multiply the weight of starter you keep by the flour part and by the water part. Keeping 50 g of starter at a 1:4:4 ratio means adding 200 g flour and 200 g water, for 450 g total. This calculator does that arithmetic and reports the final hydration of the fed starter.
What hydration is my starter?
Starter hydration is its water weight divided by its flour weight. A 1:1 flour-to-water feeding gives a 100 percent hydration liquid starter. A stiff starter might be fed at 100 g flour to 50 g water, which is 50 percent hydration. Enter the flour and water parts to see the resulting hydration.
Why does the existing starter affect the result?
Your kept starter already contains flour and water. The calculator adds the carried-over flour and water (split by the starter's own hydration) to the freshly added amounts when reporting total flour, total water and overall hydration, so the figure reflects the whole fed mixture, not just the new additions.
How often should I feed?
A starter kept at room temperature is usually fed once or twice a day; a refrigerated starter is fed roughly weekly and refreshed before baking. Larger feeding ratios such as 1:5:5 stretch the time between peaks. Feeding schedules are a craft preference, so adjust to your kitchen temperature and routine.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.