Sourdough Hydration Calculator

How It Works

Bakers work in baker's percentages — each ingredient expressed as a percentage of total flour weight rather than of total dough weight. Flour is always 100%, and everything else (water, salt, starter, additions) scales relative to it. A "75% hydration" dough means 75 g of water per 100 g of flour, not 75% water by total mass.

This convention scales cleanly: doubling a recipe means doubling the flour and every percentage stays the same. But it hides a complication that trips up sourdough bakers — the starter contains both flour and water, so a naive "500 g flour + 375 g water = 75% hydration" recipe with 100 g of 100%-hydration starter has more flour and more water than the numbers imply.

The calculator handles this using the standard equations from Ken Forkish's Flour Water Salt Yeast, Ch. 3: Baker's Percentages, and Chad Robertson's Tartine Bread, Ch. 2: Country Bread:

• Total flour = recipe flour + starter × starter_flour_fraction
• Total water = recipe water + starter × starter_water_fraction
• True hydration = total water / total flour × 100

For a 500 g flour + 375 g water recipe (nominal 75% hydration) with 100 g of 100%-hydration starter (50 g flour, 50 g water), the true hydration is:

• Total flour: 500 + 50 = 550 g
• Total water: 375 + 50 = 425 g
• True hydration: 425 / 550 = 77.3%

That's 2.3 percentage points higher than the nominal 75% — enough to change dough feel from firm to slack. The calculator computes this correction automatically.

Different flours absorb differently. Whole wheat absorbs 10-15% more water than white bread flour due to bran content; T80 and other partial whole-wheat flours sit in between; rye can absorb 20-30% more. The tool applies an absorption correction so a "78% hydration" whole-wheat dough feels similar to a 75% hydration white dough.

How to Use This Calculator

1. Enter recipe flour weight — in grams. Split by flour type if the recipe uses a blend (white bread flour, whole wheat, rye).
2. Enter recipe water weight — in grams. This is added water only, not including any water in the starter.
3. Enter starter weight and hydration — total weight of the levain plus its hydration percentage (100% means equal parts flour and water; 50% is stiff; 125% is loose).
4. Enter salt weight — in grams. Typical is 2% of flour (about 10-12 g for a 500 g flour recipe).
5. Read the true hydration — including starter contributions. The tool reports both nominal and true hydration.
6. Adjust as needed — if true hydration is higher than target, reduce recipe water; if lower, add water.

Real-World Use Cases

Standard 75% country loaf

A home baker has a 500 g flour recipe at nominal 75% hydration (375 g water) with a 100 g starter at 100% hydration. The tool reports true hydration is 77.3% — not 75%. To hit an actual 75% hydration, she reduces the recipe water to 362.5 g so total water (362.5 + 50 = 412.5 g) divided by total flour (550 g) equals 75%. Small adjustment, meaningful difference in dough feel and crumb.

High-hydration ciabatta

A baker pushes hydration to 82% for an open-crumb ciabatta with 400 g bread flour, 328 g water, and 80 g of 100% starter. True hydration: (328 + 40) / (400 + 40) = 83.6%. When she swaps to T80 flour (higher absorption ~1.05× multiplier), the effective hydration drops to about 79.6%. The tool exposes both numbers so she can adjust water accordingly.

Bagel formula

A bagel maker uses a low-hydration dough (~55% nominal) with 500 g flour, 275 g water, and 50 g of 100% starter. True hydration: (275 + 25) / (500 + 25) = 57.1%. Because bagels need a specific stiffness for proper shaping, that ~2% swing matters. The tool flags the difference so the baker can tune recipe water down if the dough tests too slack in mixing.

Tips & Safety Notes

• Weigh your starter accurately. A ±5% error on 100 g of starter shifts true hydration by roughly 0.25%, which is small — but errors compound with recipe water errors, so both need to be precise.
• Use the same starter every bake. If your starter's hydration drifts (some bakers feed at 100%, some at 125%), the true hydration of a "same" recipe will drift with it. Keep the starter maintenance protocol consistent.
• Autolyse before adding starter and salt for high-hydration doughs. Letting flour and water rest 30-60 minutes before mixing improves gluten development and lets whole-wheat bran absorb water fully.
• Salt at 2% of flour weight is the standard for savory doughs. Below 1.8% the dough over-ferments and tastes flat; above 2.5% the dough tightens and slows.
• Cover during bulk fermentation. Uncovered dough forms a skin that resists shaping and traps CO₂ unevenly.

Limitations & What This Tool Cannot Do

• No absorption modeling for arbitrary flours. The tool applies a coarse absorption correction for whole wheat and rye based on published averages, but individual mills and crop years differ. If your specific flour absorbs unusually much or little, adjust the multiplier from experience or hold back 5-10% of the recipe water and add it in during mixing based on dough feel.
• Salt and enrichment. Egg, butter, and milk in enriched doughs contribute water (about 75% water by weight for egg and milk); the tool does not automatically split these ingredients. For brioche, challah, or milk breads, treat those ingredients as separate water inputs.
• Levain-specific. Only handles a single starter or levain. Recipes with a poolish plus a levain plus a soaker need multi-preferment math not covered here — those tend to be enriched or specialty formulas where hand accounting of each preferment is the standard practice anyway.

FAQ

What is baker's percentage and why is it different from a percentage of total weight?

Baker's percentage expresses every ingredient as a percentage of total flour weight, not total dough weight. Flour is always 100%. Water at 75% means 75 g of water per 100 g of flour. This convention scales cleanly and communicates dough characteristics (a "78% hydration" is understood by any baker as an open-crumb-suitable dough) that percent-of-total wouldn't.

Why do I need to account for the flour and water inside my starter?

Sourdough starter is roughly half flour and half water (for a typical 100% hydration starter). Adding 100 g of starter to your dough adds 50 g of flour and 50 g of water to the totals — enough to noticeably shift true hydration and gluten development. Nominal hydration ignores this; true hydration includes it.

What hydration range is typical for country loaves, ciabatta, and bagels?

Country loaves run 72-78% hydration. Ciabatta and other open-crumb breads push to 78-85%. Baguettes sit around 65-72%. Bagels and other dense breads use 55-62%. Enriched breads (brioche, challah) run 55-65% because the fat, egg, and sugar limit gluten development.

Does whole wheat flour need more water than white flour?

Yes. Whole wheat absorbs 10-15% more water because the bran and germ pull water out of the dough as they hydrate. A "75% hydration" whole wheat dough feels like a ~65% hydration white dough. Bake formulas typically show a higher nominal hydration for whole wheat than for white to compensate.

How does salt affect hydration measurements?

Salt itself contributes almost nothing to the water/flour ratio at typical 1.5-2.5% levels. What salt does affect is dough feel — higher salt levels tighten gluten and make a given hydration feel drier. The calculator does not correct for this; treat salt as a separate stiffness lever.

What is the difference between actual dough hydration and "true" hydration including inclusions?

Nominal (or "recipe") hydration is water / flour based on only the explicit water and flour added to the dough. True hydration includes the water and flour hidden inside the starter, poolish, or preferment. True hydration is the number that predicts how the dough will feel and behave — nominal is the number that fits a recipe card.

Related Tools

• Brewing ABV Calculator — Adjacent ferment math for a different microbial community
• Charcuterie Cure Calculator — Adjacent food-science with different tolerances
• Coffee Extraction Calculator — Same-lab analytics

References

• Ken Forkish, Flour Water Salt Yeast, Ch. 3: Baker's Percentages — foundational hydration math
• Chad Robertson, Tartine Bread, Ch. 2: Country Bread — high-hydration technique and starter contribution accounting
• King Arthur Baking Company baker's percentage reference (kingarthurbaking.com/learn) — practical absorption tables by flour type

Reviewed by the Craft Calc Lab team on August 4, 2026.