Sourdough Starter Build Calculator
Find flour and water additions when retained seed and final starter have different hydrations.
YOUR CALCULATION
Result
—
Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Separate seed flour and water, then subtract them from final flour and water requirements.
Final flour=target mass/(1+target hydration); add flour=final flour−seed flour
Worked example
300 g of 100% hydration starter retaining 50 g of 100% seed needs 125 g flour and 125 g water.
Assumptions and input details
Seed is modeled as flour plus water only. Hydration is water mass divided by flour mass. Targets requiring negative additions are rejected. This is a single flour/water build, without fermentation time, feeding recommendation, temperature or microbial prediction.
References: King Arthur Baking: hydration is water relative to flour
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
The 19 mass definitions distinguish avoirdupois and troy measures, metric and regional measures. Japanese kin is 600 g; mainland Chinese shijin is 500 g.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
Calculate total-flour baker’s percentages and dough hydration, including a flour-and-water starter. Scale the same formula to a target dough mass.
Scale every ingredient from the original servings to a new serving count. Enter fractions, select each ingredient’s units and inspect a complete quantity table.
Convert pounds, kilograms, ounces, stone and explicitly identified ton and troy units.
Reserved advertising space.