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Sourdough Starter Calculator

Calculate how much starter, flour, and water to use when feeding your sourdough starter at a given ratio.

Result

Starter Needed
67 g
Flour Needed
67 g
Water Needed
67 g

Assumes 100% hydration (equal flour and water by weight), the most common home baking standard.

About the Sourdough Starter

Feeding a sourdough starter means combining existing starter with fresh flour and water in a specific ratio - the ratio determines how much food the starter has relative to its size, which controls how fast it becomes active.

How It Works

The calculator takes your chosen ratio (like 1:2:2, meaning 1 part starter to 2 parts flour to 2 parts water) and your desired total weight, splits the total into that many equal parts, and reports how much of each component to combine.

part weight = total weight ÷ (starter parts + flour parts + water parts)

Examples

Standard daily feeding

200g total at a 1:1:1 ratio splits into about 67g starter, 67g flour, and 67g water.

Once-daily feeding schedule

300g total at a 1:5:5 ratio splits into about 27g starter, 136g flour, and 136g water - much more food relative to the starter, so it takes longer to peak.

Advantages

  • Works for any total weight and any of the three common feeding ratios
  • Assumes the standard 100% hydration most home bakers use
  • Splits the math instantly instead of doing fraction arithmetic by hand

Common Mistakes

  • Feeding inconsistent ratios day to day, making the starter's activity unpredictable
  • Not scaling starter, flour, and water together when changing total batch size
  • Confusing a feeding ratio with a hydration percentage - they answer different questions

Edge Cases to Watch For

  • This assumes 100% hydration - equal weights of flour and water - which is the most common home baking starter consistency; a stiffer or wetter starter would need different flour and water proportions.
  • A larger ratio (like 1:5:5) gives the starter more food relative to its size and takes longer to become fully active, useful for once-daily feeding; a smaller ratio (1:1:1) becomes active faster but needs more frequent feeding.
  • Discarding starter before feeding (rather than feeding the full amount) is a separate practice some bakers use to manage starter volume - this calculator assumes you're feeding all of your existing starter.

Common Use Cases

  • Setting up a consistent daily or twice-daily feeding schedule
  • Scaling a starter up before a big baking day
  • Switching feeding ratios to change how often the starter needs attention
Written & fact-checked by the Calculateus TeamLast updated August 5, 2026How we verify our formulas

Frequently asked questions

What does a 1:2:2 ratio mean?

For every 1 part (by weight) of existing starter, you add 2 parts fresh flour and 2 parts water - a higher ratio like 1:5:5 gives the starter more food relative to its size, so it takes longer to become fully active, which is useful for once-a-day feeding schedules.

Why are flour and water equal in this calculator?

This assumes 100% hydration - equal weights of flour and water - which is the most common starter consistency for home baking. If your starter uses a different hydration level, scale the flour and water amounts from this calculator's result accordingly.

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Conclusion

A feeding ratio is really just three numbers that need to stay proportional to each other - get the math right once and every future feeding is just a multiplication away. Consistency in the ratio matters more than the specific ratio chosen, since that's what makes a starter's rise time predictable.