Sourdough Starter Calculator

Three calculation modes cover the arithmetic behind feeding, scaling, and adjusting a sourdough starter, each returning the exact flour and water amounts for the situation. Inputs accept whole numbers, decimals, fractions such as 3/4, and mixed numbers such as 1 1/2, matching whatever measurement style a recipe uses.

• Maintain Existing Starter: A feeding ratio, such as 1:1:1 or 1:2:2 for starter to flour to water, applies against the current starter weight to give the flour and water needed at the next feeding.
• Scale to Target Amount: The flour and water needed to reach a target final weight are computed while preserving the chosen starter, flour, and water ratio.
• Adjust Hydration Level: A starter converts from one hydration percentage to another, reporting how much water to add or remove.

• Maintenance feed: flour to add = current starter weight × (flour ratio ÷ starter ratio); water to add follows the same pattern with the water ratio.
• Scaling: flour or water needed = target weight × (flour or water ratio ÷ total ratio), where total ratio = starter + flour + water.
• Hydration: flour weight = starter weight ÷ (1 + hydration percent ÷ 100); target water weight = flour weight × (target hydration percent ÷ 100).

Units switch between grams, ounces, and cups. A step-by-step view shows each formula and substitution behind the result, useful for verifying a recipe or teaching baker's percentages.

Reach for these calculations any time a recipe, feeding schedule, or hydration target requires precise flour and water amounts derived from a current starter weight.

• Daily home feeding: A small 30 to 60 gram starter maintained on a 1:1:1 ratio needs no manual arithmetic each morning.
• Recipe scaling: Building a levain for a specific bread recipe starts from the target weight and chosen ratio, giving the flour and water to add.
• Hydration conversion: A 100 percent hydration starter switches to a stiffer 60 to 80 percent starter for recipes that call for a firm levain, or moves in the other direction for liquid starters.
• Bakery production: A small maintenance starter scales up to multi-kilogram production weights while keeping the original ratio intact, readable in grams or ounces.
• Travel and storage: The flour and water needed to revive a dehydrated or refrigerated starter back to a working hydration compute before a bake.
• Multi-flour starters: Separate whole wheat, rye, and white flour starters each track their own feeding ratio and hydration level.
• Teaching baker math: Starter, flour, and water ratios convert into real gram weights, with the step-by-step view showing each formula and substitution.
• Troubleshooting: Stiffer or wetter feedings can be tested when a starter is sluggish or overly acidic, showing the resulting weights before mixing.
• Class instruction: Ratio changes play out in real time during a sourdough workshop, swapping flour weights and watching every dependent value update at once.

Healthy starters double in volume within four to twelve hours after feeding at room temperature, depending on flour type, hydration, and ambient temperature. Use these calculations as a planning aid alongside visual cues like rise, smell, and bubble structure rather than replacing them. When refrigerating between bakes, plan two or three room-temperature feedings before a bake day to bring the starter back to peak activity, and recompute each time the target weight or ratio changes.