Sourdough Starter Ratio Calculator

Build starter feeds with clear ratios and hydration. Tune flour blends for vigor. Keep cultures stable through seasonal garden kitchens, day after day.

Calculator inputs
Use ratios, hydration goals, and flour blends for a steady culture.
Choose whether to match a final weight or keep a fixed seed.
Parts scaling is quick. Hydration mode honors hydration precisely.
How much starter you can spare for this feed.
Total starter after feeding (seed + flour + water).
Common starters are often near 100% hydration.
Used in hydration mode and shown as a check in parts mode.
Use parts method for classic feeds like 1:3:3.
Only used when preset is set to custom.
Used for a rough peak-time estimate.
Only splits the added flour, not the seed flour.
Custom blend is used only when selected above.
Useful for kitchen scales and tidy notes.
Saved into the session with your last result.
Tip: In parts mode, the ratio scales everything. In hydration mode, hydration and final total drive the math.
Formula used
This tool supports two calculation methods. Both are weight-based.
1) Ratio parts scaling
Ratio is starter : flour : water in parts. If seed kept is S and ratio parts are pS, pF, pW, then scale is S / pS. Added flour is pF × scale, added water is pW × scale.
2) Hydration-based build
Hydration H means water ÷ flour. Seed flour is seed/(1+Hs). Seed water is seed minus seed flour. For target total T and target hydration Ht, added flour is (T - seed - Ht×seedFlour + seedWater)/(1+Ht). Added water is Ht×(seedFlour+addedFlour) - seedWater.
How to use this calculator
  1. Enter how much starter you can use as the seed.
  2. Set your desired final total starter weight.
  3. Pick a method: ratio parts for classic feeds, or hydration-based for precision.
  4. Choose a ratio preset, or enter a custom starter:flour:water ratio.
  5. Select a flour blend to split the added flour for your routine.
  6. Press Calculate to see amounts, then download CSV or PDF.
Example data table
Scenario Inputs Outputs
Daily refresh Seed 25g, ratio 1:3:3, parts method Add 75g flour, 75g water, total 175g
Build for baking Seed 30g, target total 240g, ratio 1:3:3 Keep 34.3g seed, add 102.9g flour and 102.9g water
Stiffer culture Seed 25g at 100%, target 200g, hydration mode 70% Adds computed to hit 70% hydration and target mass
Note: Example values are illustrative. Your results may differ after rounding.

Why starter ratios matter in garden kitchens

Ratio planning controls how fast your culture ferments and how predictable your bake schedule becomes. A higher feed ratio dilutes acidity and slows activity, which helps during warm afternoons. A lower ratio increases inoculation, rises quicker, and suits cooler mornings and short proof windows. The calculator reports inoculation percent so you can repeat outcomes across changing seasons.

Hydration targets and texture control

Hydration defines starter consistency, handling, and gas retention. At 100% hydration, equal flour and water create a spoonable paste that ferments evenly. Stiffer builds near 60–80% hold shape, favor lactic balance, and peak with a narrower window. The hydration-based method uses seed hydration to estimate seed flour and water, then solves additions to meet your target.

Flour blend strategy for steady vigor

Flour choice affects minerals, enzymes, and microbial diversity. White flour keeps flavors mild and makes timing consistent. Whole wheat adds nutrients that accelerate activity, especially after a cold night. Rye often boosts fermentation and aroma, but can run fast in heat. Use the blend splitter to distribute added flour by percent, keeping your routine consistent even when scaling.

Temperature and peak-time expectations

Temperature is the biggest driver of speed. Warmer rooms shorten peak time and can exaggerate sourness if the starter over-ferments. Cooler spaces slow rise and may require higher inoculation or a smaller feed ratio. The estimate shown is a planning hint, not a guarantee; always confirm with volume increase, bubbles, and aroma. Recording the displayed hours alongside your notes builds a reliable personal dataset.

Scaling, rounding, and waste reduction

Scaling by parts keeps proportions stable, while rounding keeps the plan realistic for kitchen scales. Choose a rounding increment that matches your measurement accuracy to reduce frustration and waste. If you maintain multiple jars, the target-total mode helps you build exactly what you need for baking and storage. Downloading CSV or PDF creates a repeatable log that supports consistent results week after week.

FAQs

1) What does a 1:3:3 feed mean?

It means one part starter is fed with three parts flour and three parts water. If you keep 25g starter, you add 75g flour and 75g water.

2) Which method should I choose?

Use ratio parts for quick, classic feeds and easy scaling. Use hydration-based when you must hit a specific hydration or when your seed hydration is not standard.

3) Why do I need seed hydration?

Seed hydration lets the calculator estimate how much flour and water already exist in your starter. That improves hydration accuracy and makes results more consistent when you change seed amounts.

4) How do I adjust for hot weather?

Increase the feed ratio (more flour and water per starter) or lower inoculation to slow fermentation. You can also ferment cooler or shorten the time between feeds.

5) Can I use the flour blend split with any recipe?

Yes. The blend feature only splits the added flour for your feeding. It does not change the seed composition, so it works with most routine maintenance and build schedules.

6) Why does my peak time differ from the estimate?

Peak depends on starter strength, flour type, water chemistry, and jar shape. Use the estimate as a planning baseline, then refine it using your observations and repeatable notes.

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