Sourdough Starter Ratio Calculator Formula

Understand the math behind the sourdough starter ratio calculator. Each variable explained with a worked example.

Use the Sourdough Starter Ratio Calculator

Formulas Used

Flour to Add

flour_add = starter_amount * ratio_flour

Water to Add

water_add = starter_amount * ratio_water

Total After Feeding

total_after = starter_amount + (starter_amount * ratio_flour) + (starter_amount * ratio_water)

Starter Hydration

hydration = (ratio_water / ratio_flour) * 100

Variables

VariableDescriptionDefault
starter_amountExisting Starter to Keep(g)50
ratio_flourFlour Ratio Part1
ratio_waterWater Ratio Part1

How It Works

How to Feed Sourdough Starter

Formula

A 1:1:1 feeding means equal parts starter, flour, and water by weight.

Flour to Add = Starter x Flour Ratio Water to Add = Starter x Water Ratio

Common Ratios

  • 1:1:1 - Standard daily feeding
  • 1:2:2 - For slower fermentation / cooler environments
  • 1:5:5 - For very long fermentation schedules
  • 1:3:3 - Good for overnight rise

    • Worked Example

    Feed 50 g of starter at a 1:1:1 ratio.

    starter_amount = 50ratio_flour = 1ratio_water = 1
    1. 01Keep 50 g of starter.
    2. 02Add flour: 50 x 1 = 50 g.
    3. 03Add water: 50 x 1 = 50 g.
    4. 04Total: 50 + 50 + 50 = 150 g at 100% hydration.

    Ready to run the numbers?

    Open Sourdough Starter Ratio Calculator