Sourdough Baking by the Numbers: Hydration, Timing, and Temperature
Master sourdough bread with data-driven precision. Covers hydration percentages, starter feeding ratios, bulk fermentation timing, and how temperature affects every stage of the process.
Why Numbers Matter in Sourdough Baking
Sourdough baking is often described as an art, but the best bakers treat it as applied science. Every variable, from hydration percentage to ambient temperature, has a measurable effect on the final loaf. Understanding these numbers takes the guesswork out of baking and makes your results repeatable.
The two most important calculations are hydration (the ratio of water to flour) and inoculation (how much starter you add relative to flour). Our Sourdough Hydration Calculator handles both, giving you exact weights for flour, water, starter, and salt at any hydration level.
Understanding Hydration Percentages
Hydration is expressed as a baker's percentage: the weight of water divided by the weight of flour, multiplied by 100. Here is how different hydration levels affect your bread:
| Hydration | Dough Feel | Crumb Structure | Best For |
|---|---|---|---|
| 60 to 65% | Stiff, easy to shape | Tight, even | Sandwich bread, bagels |
| 68 to 72% | Moderate, beginner-friendly | Medium openness | All-purpose artisan loaf |
| 75 to 78% | Tacky, needs bench rests | Open, irregular holes | Classic sourdough boule |
| 80 to 85% | Wet, advanced handling | Very open, large holes | Ciabatta, focaccia |
Note that flour type also matters. Whole wheat and rye absorb more water, so increase hydration by 5 to 10% when using these flours. Our calculator adjusts for starter hydration automatically.
Starter Feeding Ratios and Peak Timing
Your sourdough starter (levain) is a living culture of wild yeast and lactic acid bacteria. The feeding ratio determines how fast it ferments and when it peaks:
- 1:1:1 (equal parts starter, flour, water): Peaks in 4 to 6 hours at 22 degrees Celsius. Good for same-day bakes.
- 1:3:3: Peaks in 8 to 10 hours. Good for morning feeds with afternoon bakes.
- 1:5:5: Peaks in 12 to 16 hours. Perfect for overnight levains.
Use our Sourdough Starter Feeding Calculator to get exact flour and water weights for any feeding ratio, with estimated peak times.
The Role of Temperature in Fermentation
Temperature is the invisible hand controlling every stage of sourdough baking. Here is a quick reference:
| Temperature | Bulk Fermentation Time (approx.) | Flavor Profile |
|---|---|---|
| 18 to 20 degrees Celsius | 8 to 12 hours | More complex, mild tang |
| 22 to 24 degrees Celsius | 4 to 6 hours | Balanced flavor, moderate tang |
| 26 to 28 degrees Celsius | 2 to 4 hours | Faster fermentation, more lactic acid |
Cold retarding (placing shaped dough in the fridge at 3 to 5 degrees Celsius for 12 to 48 hours) slows fermentation dramatically and develops deeper, more complex flavors. Most artisan bakeries use an overnight cold retard before baking.
Salt: The Small Ingredient with Big Impact
Salt is typically added at 2% of flour weight (10 grams of salt for 500 grams of flour). It serves three critical functions: strengthening the gluten network for better structure, controlling fermentation speed by inhibiting enzyme activity, and enhancing flavor. Without salt, your dough will ferment too quickly and the bread will taste flat.
Add salt after the autolyse (initial mixing of flour and water) to allow gluten to develop first. This technique, combined with proper hydration, produces the best crumb structure.
Putting It All Together: A Sample Bake Schedule
Here is a typical schedule for a 75% hydration sourdough loaf using 500 grams of flour at 22 degrees Celsius room temperature:
- 8:00 AM: Feed starter at 1:5:5 ratio (or use a levain built the night before at 1:5:5 that has peaked overnight).
- 9:00 AM: Autolyse flour and water for 30 to 60 minutes.
- 10:00 AM: Add starter and salt. Mix until incorporated.
- 10:00 AM to 2:00 PM: Bulk fermentation with 3 to 4 sets of stretch-and-folds every 30 minutes during the first 2 hours.
- 2:00 PM: Pre-shape. Bench rest 20 minutes. Final shape and place in banneton.
- 2:30 PM to next morning: Cold retard in the fridge.
- Next morning: Preheat oven with Dutch oven to 250 degrees Celsius. Bake 20 minutes covered, 20 to 25 minutes uncovered at 230 degrees Celsius.
Use our Sourdough Hydration Calculator to get the exact gram amounts for this recipe at any dough weight.
Frequently Asked Questions
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