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.

    Frequently Asked Questions

    What does 1:1:1 mean?

    It means 1 part starter, 1 part flour, 1 part water by weight. So 50 g starter + 50 g flour + 50 g water. This is the most common feeding ratio.

    When should I use a higher feeding ratio?

    Use 1:2:2 or higher in warm weather, or when you want the starter to peak later (such as overnight). Higher ratios give the yeast more food and slow the rise.

    What is starter hydration?

    Starter hydration is the water-to-flour ratio. A 1:1 water-to-flour ratio gives 100% hydration. Some bakers maintain stiff starters at 50-60% hydration.

    Ready to run the numbers?

    Open Sourdough Starter Ratio Calculator