Sourdough Hydration Calculator 💧

Free sourdough hydration calculator. Enter flour, water, and starter amounts to calculate overall dough hydration including the water content in your starter.

The Sourdough Hydration Calculator gives you the true overall hydration of a sourdough or naturally leavened bread by including the flour and water trapped inside your starter or levain. Most beginner sourdough recipes only divide added water by added flour and ignore the starter — which can underreport hydration by 5–10 percentage points and explain why a recipe written as 70% hydration handles like 78%. Enter the flour you're adding directly, the water you're adding directly, the starter weight, and the starter's hydration (typically 100% for a liquid starter, 50% for a stiff starter, 60% for a Tartine country levain). The calculator splits the starter into its constituent flour and water, sums the totals, and returns the true dough hydration. This is the same math used in every modern sourdough textbook and is critical when you scale a recipe from one batch size to another.

How to Use the Sourdough Hydration Calculator

  1. Enter Flour and Water — Enter the weight of flour and water you're adding directly to the recipe.
  2. Enter Starter Info — Enter the starter weight and its hydration percentage. A 100% hydration starter means half its weight is water.
  3. Read Overall Hydration — The overall dough hydration including starter water is calculated automatically.
  4. Compare to Target — If overall hydration is below your target (say 75%), increase added water in 1–2% steps. If above, hold back 5–10g of water during mixing and adjust by feel.
  5. Plan Salt and Levain Percentages — Salt should be 1.8–2.2% of total flour. Levain is typically 15–25% of total flour weight — adjust based on temperature and timing of bulk fermentation.

Formula Reference

Starter water = starter weight × hydration ÷ (100 + hydration). Starter flour = starter weight − starter water. Total flour = added flour + starter flour. Total water = added water + starter water. Overall hydration % = (total water ÷ total flour) × 100. Example: 800g flour + 560g water + 200g starter at 100% hydration → starter contributes 100g flour and 100g water, so total flour = 900g, total water = 660g, overall hydration = 73.3%.

Source: Chad Robertson, Tartine Bread (Chronicle Books, 2010); Ken Forkish, Flour Water Salt Yeast (Ten Speed Press, 2012); Nathan Myhrvold, Modernist Bread (The Cooking Lab, 2017) — Sourdough volume.

FAQ

What does 100% starter hydration mean?

A 100% hydration starter contains equal parts flour and water by weight. For example, 200g starter = 100g flour + 100g water.

What is the ideal sourdough hydration?

65–70% is recommended for beginners. As you gain experience, increase to 75–80% for a more open crumb and crispier crust.

Why does my sourdough feel wetter than the recipe says?

Because the recipe probably ignored starter water. A recipe that lists 70% added water plus a 20% inoculation of 100% starter actually runs at about 75% true hydration. Use this calculator to see the real number.

How do I convert a stiff starter to a liquid starter in a recipe?

Calculate the flour and water in the stiff starter (50% hydration = 1/3 water, 2/3 flour). Replace it with the same total weight of liquid starter, but rebalance added water and flour so the total flour and water counts stay the same. The calculator handles this automatically when you change the starter hydration field.

Does whole wheat absorb more water than bread flour?

Yes — whole wheat absorbs roughly 5–10% more water than white bread flour because of bran and germ. A 75% hydration recipe with 20% whole wheat behaves more like 78–80% hydration in handling. Reduce added water by 2–3% if you're new to whole grain sourdough.

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