Sourdough Hydration & Timing Calculator

Sourdough Baking Guide

What's the key thing to understand about Understanding Hydration?

Sourdough hydration is water as a percentage of flour by weight. 65–70%: beginner-friendly, easier to shape, tight crumb structure. 72–76%: balanced — the classic country loaf range, open crumb, good rise. 78–85%: high hydration, more open crumb, more challenging to handle. 85%+: very slack dough, requires good technique, typically baked in a tin. Starter hydration also affects the total — if using a 100% hydration starter (equal weights flour and water), half the starter weight counts as water.

What's the key thing to understand about Temperature and Fermentation?

Fermentation rate roughly doubles for every 10°C rise in temperature (Q10 rule). At 18°C, bulk fermentation may take 12 hours. At 24°C, the same dough may be ready in 4–5 hours. This is why recipes saying 'bulk ferment for X hours' are unreliable without knowing room temperature. A dough thermometer is more useful than a clock. Look for 50–75% increase in volume, a domed surface with bubbles, and a jiggly but not slack texture.

What's the key thing to understand about The Fold and Coil Process?

Rather than kneading, sourdough develops structure through a series of stretch-and-fold or coil-fold sets during bulk fermentation. Typically 4–6 sets in the first 2 hours, then leaving the dough alone to ferment fully. Each fold builds gluten structure and traps gas. Under-folding produces a flat, dense loaf. Over-folding can degas the dough. The dough should feel noticeably stronger and more cohesive after the first few folds.

What should I know about The Bake — Dutch Oven Method?

Baking in a preheated Dutch oven (lidded cast iron) traps steam from the dough, producing an open ear and blistered, crackled crust — the hallmark of a good sourdough. Preheat the Dutch oven in a 250°C oven for 45–60 minutes. Bake covered for 20 minutes (steam phase), then remove lid and bake at 220°C for a further 20–25 minutes until deep mahogany brown. Internal temperature should reach 96–98°C. Let cool for at least 1 hour before cutting — the crumb continues setting as it cools.

What should I know about How Room Temperature Changes Your Timeline?

The room_temp_c you enter has an outsized effect on bulk_duration because fermentation is a temperature-driven chemical process: as a rough practical guide, fermentation activity roughly doubles for every 8–10°C rise in dough temperature, within the normal kitchen range. This means a dough bulk fermenting at a cool 18°C can easily take twice as long (or more) to reach the same level of development as the identical dough at a warmer 26°C. This is why this calculator asks specifically for room temperature rather than giving one fixed bulk fermentation time for all conditions — a schedule built for a warm summer kitchen would badly underproof a dough made in a cool winter kitchen, and vice versa a schedule built for winter would risk overproofing in summer. If your kitchen temperature swings meaningfully between morning and evening, or between seasons, it's worth re-checking this input and the resulting bake_time and fold_schedule each time rather than reusing a schedule that worked previously under different conditions.

What should I know about Reading Dough Instead of the Clock?

The bulk_duration, fold_schedule, and bake_time outputs from this calculator are genuinely useful planning estimates built from your inputs, but sourdough fermentation is variable enough that the dough itself remains the most reliable final judge of readiness. The classic visual and tactile signs that bulk fermentation is complete are roughly a 30–50% increase in dough volume from where it started, a slightly domed and jiggly surface when the container is gently shaken, and visible bubbles at the surface and sides of a clear container, rather than any single elapsed-time number. Starter strength, flour type, exact starter_grams used, and even small day-to-day temperature fluctuations in a kitchen can shift actual fermentation time earlier or later than a calculated estimate. Treat the schedule from this calculator as a strong starting point for planning your day around (when to fold, roughly when to expect the dough ready to shape, roughly when you'll be baking) but check the dough's actual appearance and feel at the point the estimate suggests it should be ready, and adjust from there if needed.

What do I need to know about the Float Test and Other Starter Readiness Checks?

The float test — dropping a small spoonful of active starter into a glass of water and checking whether it floats — is a popular quick check for whether a starter has enough gas production to be ready for baking, but it's not fully reliable on its own and is best used alongside other visual cues. A starter that floats generally has enough carbon dioxide trapped in its structure to be buoyant, suggesting good yeast activity, but a starter that sinks isn't necessarily unusable — it may simply have a looser, less gas-retentive structure (common with very high-hydration or well-fed, very active starters that have already partially deflated) despite still being perfectly capable of raising a dough. More reliable readiness indicators include visual doubling or more in volume within a predictable window after feeding, a domed rather than flat or concave surface, visible bubbles throughout rather than just on top, and a pleasant, mildly tangy or yeasty smell rather than a harsh vinegar or acetone smell (which suggests it's past peak and hungry). The most dependable approach combines several checks together — doubling time, surface appearance, smell, and optionally the float test — rather than relying on any single indicator, since starters vary in consistency and behaviour even when equally healthy and ready to use.

Worked Example: Adjusting Bulk Fermentation for a Warm Kitchen

A standard sourdough recipe might call for a 4-hour bulk fermentation at 24°C room temperature. Fermentation rate roughly doubles for every 8–10°C rise in temperature within the normal baking range, so the same dough left in a kitchen at 30°C (a plausible summer temperature) could reach the same degree of fermentation in closer to 2.5–3 hours rather than 4 — meaning a baker following the clock rather than watching the dough risks badly over-fermenting it on a hot day. Conversely, a cooler kitchen at 18°C might need 5.5–6 hours to reach the same point. This is why experienced sourdough bakers treat stated times as a starting estimate for their specific kitchen and season, then use visual and tactile cues — dough volume increase, surface bubbles, and a gentle jiggle test for wobble — to judge true readiness.

How Does Starting Dough Temperature Affect the Timeline?

Water temperature used when mixing the dough has an outsized effect on these figures because it sets the dough's starting temperature before ambient room temperature takes over more slowly; bakers in warm climates often deliberately use cooler (even refrigerated) water to slow the dough down to a manageable pace, while bakers in cold kitchens sometimes use slightly warmer water for the opposite reason. The relative speed figures above are a general guide rather than a precise multiplier, since the specific starter's activity level and the dough's exact hydration also change how quickly fermentation proceeds. Refrigerating the shaped dough overnight (a 'cold retard') is a separate technique from adjusting the bulk fermentation time, and is commonly used specifically to slow fermentation down enough to bake at a convenient time the next morning rather than needing to bake the same evening the dough is mixed.

What should I know about Autolyse and Why It's a Separate Step From Fermentation?

An autolyse — resting flour and water together, without the starter, for 20 minutes to an hour before mixing in the starter and salt — is a separate technique from the fermentation timing covered elsewhere on this page, though the two are often confused by newer bakers. During autolyse, enzymes naturally present in the flour begin breaking down starches and strengthening gluten structure before fermentation even begins, which can make the dough easier to handle and improve the final crumb structure. Because no starter is present yet, no meaningful fermentation happens during an autolyse, so it should be timed and thought about separately from the bulk fermentation clock, even though both steps happen early in the overall sourdough timeline. Some bakers extend autolyse well beyond an hour, even overnight in the fridge, for extra gluten development, though very long autolyse times need the dough kept cold specifically to avoid unwanted fermentation starting from any wild yeast or bacteria naturally present in the flour itself.