TL;DR
Sourdough hydration is the ratio of water to flour in your dough, expressed as a percentage using baker’s math. A 75% hydration dough contains 750 g of water for every 1000 g of flour. The tricky part: your sourdough starter (levain) contains both flour and water, which must be factored into the total. Hydration dramatically affects crumb structure, crust, rise, and handling difficulty. Lower hydration (60–65%) produces a tight, sandwich-friendly crumb; higher hydration (78–85%) creates the coveted open, airy crumb of artisan loaves. This guide walks you through the calculations, provides a ready-to-use calculator, and helps you troubleshoot common hydration mistakes.
Walk into any artisan bakery and you’ll see loaves with wildly different crumb structures — from dense, even sandwich bread to those dramatic, hole-riddled sourdough boules that look like Swiss cheese. The single biggest factor controlling that difference is hydration.
But sourdough hydration is more complex than it first appears. Unlike commercial yeast baking where you simply add water to flour, sourdough uses a living starter that itself contains flour and water in a specific ratio. Getting the math right — and understanding what different hydration levels actually mean for your dough — is essential to consistent results.
[CALCULATOR:sourdough_hydration]
What Is Baker’s Percentage?
Baker’s percentage (also called baker’s math) is the universal language of bread formulation. Every ingredient is expressed as a percentage of the total flour weight, with flour always equalling 100%.
For a simple example:
| Ingredient | Weight | Baker’s % |
|---|---|---|
| Bread flour | 500 g | 100% |
| Water | 375 g | 75% |
| Salt | 10 g | 2% |
| Starter (100% hydration) | 100 g | 20% |
This is a 75% hydration dough — at least at first glance. But wait: that 100 g of starter at 100% hydration contains 50 g of flour and 50 g of water. The true total flour in this recipe is 550 g (500 + 50), and the true total water is 425 g (375 + 50). The actual hydration is:
425 ÷ 550 = 77.3%
That 2.3% difference matters. It’s the difference between a dough that handles comfortably and one that sticks to everything. Many bakers unknowingly work at a higher hydration than they think because they forget to account for the water in their starter.
How to Calculate True Hydration
The formula is straightforward once you know the pieces:
Hydration % = (Total Water ÷ Total Flour) × 100
Where: - Total Water = recipe water + water in starter - Total Flour = recipe flour + flour in starter
The water and flour in your starter depend on the starter’s own hydration level:
| Starter Hydration | Flour in 100 g | Water in 100 g |
|---|---|---|
| 50% (stiff) | 66.7 g | 33.3 g |
| 75% | 57.1 g | 42.9 g |
| 100% (standard) | 50.0 g | 50.0 g |
| 125% (thin) | 44.4 g | 55.6 g |
| 166% (liquid/batter) | 37.6 g | 62.4 g |
Worked Example: 68% Hydration Loaf
Target: 68% hydration, 800 g total flour, using 160 g of 100% hydration starter.
Step 1: Flour and water in the starter. - 160 g starter at 100% hydration = 80 g flour + 80 g water
Step 2: Remaining flour needed. - 800 g total flour − 80 g (from starter) = 720 g recipe flour
Step 3: Total water needed. - 68% × 800 g = 544 g total water - 544 g − 80 g (from starter) = 464 g recipe water
Step 4: Verify. - Total flour: 720 + 80 = 800 g - Total water: 464 + 80 = 544 g - Hydration: 544 ÷ 800 = 68.0%
Worked Example: Converting a Stiff Starter Recipe to Liquid
Your recipe calls for 150 g of 60% hydration starter, but you maintain a 100% hydration starter. You need to adjust the recipe water and flour to compensate.
150 g of 60% hydration starter contains: - Flour: 150 ÷ 1.60 = 93.75 g - Water: 150 − 93.75 = 56.25 g
150 g of 100% hydration starter contains: - Flour: 75 g - Water: 75 g
Difference: - You’re adding 18.75 g less flour (93.75 − 75) - You’re adding 18.75 g more water (75 − 56.25)
Fix: Add 18.75 g to the recipe flour and subtract 18.75 g from the recipe water.
Hydration Levels: What to Expect
Low Hydration: 55–65%
- Crumb: Tight, even, small holes
- Crust: Thin, often soft
- Handling: Easy — dough is firm and cooperative
- Best for: Bagels (55–60%), sandwich bread, rolls, pizza Napoletana (58–62%)
- Fermentation note: Lower hydration slows fermentation slightly because water availability limits enzymatic activity
Medium Hydration: 65–72%
- Crumb: Moderately open, mix of small and medium holes
- Crust: Medium thickness, some crackle
- Handling: Manageable — slight tackiness but shapeable
- Best for: French bread, country loaves, focaccia (at the upper end), most everyday sourdough
- Fermentation note: The sweet spot for most bakers. Good balance of flavour development and workability.
High Hydration: 72–80%
- Crumb: Open, irregular holes, translucent cell walls
- Crust: Thick, crackly, deeply caramelised
- Handling: Challenging — dough is sticky, requires bench scrapers and confident technique
- Best for: Artisan sourdough boules, batards, ciabatta (78–80%)
- Fermentation note: Higher hydration promotes more Lactobacillus activity relative to yeast activity, which can produce a more complex, slightly more acidic flavour.
Very High Hydration: 80–90%+
- Crumb: Extremely open, large irregular holes, custard-like texture between holes
- Handling: Very difficult — dough behaves almost like batter; requires extensive coil folds or lamination rather than traditional kneading
- Best for: Focaccia (85–90%), ciabatta (extreme versions), Pan de Cristal
- Fermentation note: Dough strength comes almost entirely from gluten development during fermentation, not from initial mixing. Long bulk fermentation (5–8 hours at room temperature) is typical.
Flour Type and Effective Hydration
Not all flours handle the same hydration equally. The protein content and grain type dramatically affect water absorption:
| Flour Type | Protein Content | Effective Hydration Range | Notes |
|---|---|---|---|
| Bread flour (T65) | 11.5–13% | 68–80% | Standard choice for sourdough |
| All-purpose (T55) | 9.5–11.5% | 62–72% | Less gluten = less water tolerance |
| Whole wheat (T150) | 13–15% | 72–85% | Bran absorbs extra water |
| Rye flour | 8–12% | 65–80% | Pentosans absorb water differently |
| Spelt | 11–14% | 60–68% | Fragile gluten, over-hydration breaks structure |
| Semolina/durum | 12–14% | 55–65% | Very strong, low absorption |
When substituting whole wheat for bread flour, add 3–5% more water. Whole wheat bran acts like tiny sponges that absorb water over time — your dough will feel wetter initially and then firm up during autolyse and bulk fermentation.
Troubleshooting Wet Dough
High-hydration sourdough is a skill that takes practice. Here are the most common problems and their solutions:
“My dough is a sticky mess and won’t hold shape”
Possible causes: - Hydration is too high for your flour type. Drop by 3–5% and try again. - Insufficient gluten development. Perform more stretch-and-folds (4–6 sets at 30-minute intervals during bulk). - Under-fermented. Properly fermented dough gains strength; if your bulk fermentation was cut short, the dough lacks the gas structure that provides support.
“My bread spreads flat after scoring”
Possible causes: - Over-proofed (either during bulk or final proof). The gluten network has exhausted its elasticity. - Weak shaping. High-hydration doughs need firm, confident pre-shaping and final shaping to build surface tension. - Insufficient cold retard. A 12–24 hour stint in the refrigerator at 3–5 °C (37–41 °F) firms the dough and makes it much easier to score and load.
A proper proofing basket helps enormously with holding shape during the final proof. The
“My crumb is gummy even though it looks done”
Possible causes: - Under-baked. Internal temperature should reach 96–99 °C (205–210 °F). Use an instant-read thermometer. - Cut too soon. High-hydration loaves need at least 2 hours of cooling on a wire rack. The crumb continues to set as steam escapes; cutting too early releases moisture that should be leaving through the crust. - Over-fermented. An over-proofed loaf can have a gummy texture because the weakened gluten network collapses and compresses.
The Autolyse Advantage
Autolyse — mixing flour and water and resting for 30–60 minutes before adding starter and salt — is particularly valuable for high-hydration doughs. During autolyse:
- Flour fully absorbs the water (hydration becomes even throughout)
- Gluten bonds begin forming passively (reducing the mixing/kneading needed)
- Amylase enzymes begin breaking down starch into sugars (improving flavour)
- The dough becomes noticeably smoother and more extensible
For doughs above 75% hydration, autolyse transforms the experience from wrestling with sticky batter to working with a cooperative, extensible dough. Some bakers autolyse for up to 4 hours for very high hydration formulas with whole grains.
Sourdough and Other Fermented Foods
The principles of fermentation that govern sourdough — microbial cultures, temperature control, acid production, timing — connect directly to other fermented foods. If you’re interested in exploring further, our guides on Sauerkraut Fermentation Basics, Kombucha Alcohol Content Explained, and Kefir Fermentation Alcohol Content apply the same fundamental science to different culinary traditions.
Quick Reference: Common Recipes and Their Hydration
| Recipe | Total Flour | Total Water | Starter (100%) | True Hydration |
|---|---|---|---|---|
| Beginner sourdough | 500 g | 325 g | 100 g (50f + 50w) | 68.2% |
| Tartine country loaf | 700 g + 100 g WW | 525 g + 250 g | 200 g (100f + 100w) | 75.0% |
| High-hydration boule | 450 g | 360 g | 90 g (45f + 45w) | 81.8% |
| Sandwich sourdough | 500 g | 275 g | 100 g (50f + 50w) | 59.1% |
| Focaccia | 500 g | 400 g | 100 g (50f + 50w) | 81.8% |
Key Principles to Remember
- Always account for the flour and water in your starter when calculating hydration
- Start at 68–70% if you’re new to sourdough, then increase by 2–3% as your skills improve
- Adjust hydration to your flour — whole grain flours need more water, low-protein flours need less
- Temperature affects hydration perception — warm dough feels stickier than cold dough at the same hydration
- Weigh everything — volume measurements (cups, tablespoons) are hopelessly imprecise for baking. A kitchen scale accurate to 1 g is the single most important tool in bread baking
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Methodology
Baker’s percentage calculations follow the conventions established by the American Institute of Baking (AIB) and Raymond Calvel’s The Taste of Bread (Springer, 2001). Hydration level descriptions and their effects on crumb structure reference Chad Robertson’s Tartine Bread (Chronicle Books, 2010), Jeffrey Hamelman’s Bread: A Baker’s Book of Techniques and Recipes (Wiley, 3rd edition, 2012), and the King Arthur Flour/Baking Company educational resources. Flour protein ranges reference USDA FoodData Central and European type classifications (French T-numbers). Water absorption differences between flour types are based on published farinograph data from the ICC (International Association for Cereal Science and Technology). Internal bread temperatures for doneness follow recommendations from the Bread Bakers Guild of America.