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A sourdough starter isn't just flour or just water — it's itself a mix of both, typically at 100% hydration (equal parts by weight). That means it contributes both flour and water to your final dough, and ignoring that contribution understates your dough's true overall hydration.
This calculator accounts for the starter's own flour and water content when finding your dough's true overall hydration percentage.
How it works
Enter your recipe's flour and water (not counting the starter), plus your starter's weight and its own hydration percentage (100% by default, for an equal-parts starter). The tool splits the starter into its own flour and water contribution, adds those to your totals, then calculates overall hydration.
- Enter flour (g, not including starter).
- Enter water (g, not including starter).
- Enter starter (g, optional).
- Enter starter hydration % (default 100%).
- Click Calculate to see your results.
Examples
A typical sourdough loaf
500g flour, 350g water, and 100g of a 100%-hydration starter gives a true overall hydration of about 72.7% — higher than the 70% you'd get by ignoring the starter's contribution.
Who should use it
- Finding a sourdough recipe's true overall hydration for comparison with other recipes.
- Adjusting a recipe's water content while accounting for a specific starter's contribution.
Industry applications
- Home and professional sourdough baking
Advantages
- Accounts for the starter's real contribution, unlike a naive water÷flour calculation.
- Works for any starter hydration percentage, not just the common 100% default.
Limitations
- Doesn't account for other hydration sources in a recipe (like eggs or milk) — this calculates flour/water hydration specifically.
Common mistakes to avoid
- Calculating hydration as simply water ÷ flour from the recipe, ignoring the starter's own flour and water contribution.
- Assuming every starter is at 100% hydration when some bakers maintain stiffer or looser starters.
Best practices
- Know your specific starter's hydration percentage (it's simply how it's fed/maintained) rather than assuming the common 100% default if yours is different.
Tips
- Higher hydration doughs (75%+) are stickier and harder to shape but often give a more open, airy crumb — adjust your recipe's target hydration based on the texture you're after.