Sourdough Starter Feeding Calculator
Calculate starter, flour, and water for any feeding ratio (1:1:1, 1:2:2, 1:5:5).
What this calculates
A sourdough starter needs regular feeding — discard some, add fresh flour and water. The ratio of starter:flour:water determines how long until peak activity. Lower ratios (1:1:1) peak fast but exhaust quickly; higher ratios (1:5:5) take longer but hold ripeness longer, better for overnight builds.
Formula & how it works
Given target starter weight and ratio S:F:W: starter = target × S/(S+F+W). flour = target × F/(S+F+W). water = target × W/(S+F+W). Final weight = sum of inputs.
Worked example
150 g starter at 1:2:2: starter 30 g + flour 60 g + water 60 g.
Frequently asked questions
Which ratio?
1:1:1 peaks in 4-6 hr (warm kitchen). 1:5:5 in 8-12 hr — common for overnight pre-ferments.
100% hydration?
Equal flour and water by weight. Most calculators (and recipes) assume this. Stiff starters use 50-60% water.
How to know it's peaked?
Doubled in volume, dome-topped, smells tangy-sweet. Drop a spoonful in water — floats = ready.