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Sourdough Hydration Calculator

A sourdough hydration calculator treats flour as 100% baker’s percent. Water is hydration percent of that flour. Starter is a percent of flour, split into flour and water using starter hydration. Salt is a percent of flour. Dough water is reduced by the water already in the starter so total hydration stays on target.

Quick Summary & Direct Answer
Kitchen

What is 72% hydration on 500 g flour with 20% starter?

500 g flour at 72% wants 360 g water in the dough system. 20% starter at 100% hydration is 100 g starter (50 g flour + 50 g water). Bowl water is 310 g. Salt at 2% is 10 g. Total dough is 920 g and true hydration including starter flour is 65.5% (360 g water / 550 g flour).

Key Takeaways

  • Baker’s percent is always of the bread flour unless noted.
  • Starter water is subtracted from bowl water.
  • True hydration includes starter flour in the denominator.
  • Pizza and cookie baker’s percent use the same fields with different hydration.

Bowl water

310 g

Starter100 g
Salt10 g
Dough920 g
True hydration65.5%

Results can be wrong. This calculator is unofficial. Figures can be incomplete, rounded, or not updated. Use them at your own risk and check a tape, datasheet, ball band, or official chart before cutting, mixing, buying, or publishing. Hydration here is a target on bread flour, with starter water subtracted from the bowl. Other apps treat hydration as bowl water only; the two conventions disagree. Limits of liability are in the terms of service.

Frequently asked questions

This page targets hydration on bread flour, then reports true hydration of all flour including starter flour.

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Publisher notes · reviewed 29 October 2026

Bowl water subtracts starter water

Flour is 100%. Hydration is water on that flour. Starter percent is of flour and is split using starter hydration. Bowl water = flour × hydration − starter water. True hydration includes starter flour in the denominator.

Pizza and cookies

The same fields accept 60% pizza or a stiff cookie dough. Cups are not used.

Worked examples

  • 500 g flour, 72%, 20% starter at 100%, 2% salt

    Starter 100 g, bowl water 310 g, salt 10 g, dough 920 g.

Limits of this page

  • Autolyse timing is not a formula.
  • Whole-grain absorption is extra water the baker adds by feel.

Sources