How this calculator works.
Sourdough timing is governed by enzyme activity and yeast metabolism, both of which scale predictably with temperature. As a rule of thumb fermentation rate roughly doubles for every 8°C rise in dough temperature. The calculator uses that relationship, along with your inoculation percentage, to estimate bulk fermentation duration, then schedules the rest of the steps around it.
Temperature drives everything
Most kitchen sourdough disasters trace back to a single mistake: ignoring room temperature. A dough that finishes bulk in five hours at 26°C will need eight to ten at 20°C. Dough fully proofed at midnight in summer will be barely awake at midnight in winter. Measuring actual room temperature, not the thermostat, makes the difference between consistent loaves and a year of frustration.
Inoculation as a timing dial
The percentage of starter relative to total flour is the second knob you have. More starter (25–30%) accelerates bulk; less (10–15%) slows it. Bakers prefer low inoculation in summer to keep timelines manageable, and bump it up in winter when ambient temperatures drag everything out.
Cold retard isn't optional, but it is flexible
Twelve hours at 4°C develops flavor, makes scoring easier, and lets you bake in the morning instead of after midnight. Longer retards (24–36 hours) intensify tang. Skip retard entirely and you can bake same-day, but expect a tighter window between proof and overproof.
Starter readiness, decoded
Active and peaked: at least doubled, dome on top, floats in water — use within an hour of peak. Recently fed: needs four to six more hours to ripen at room temperature. Cold from fridge: warm up, feed, wait for peak — total around eight to twelve hours, sometimes split across two feeds for vigor. The Starter tab handles this math automatically.
The DDT formula
Desired Dough Temperature is a professional baker's tool for landing dough at a target temperature immediately after mixing. The formula is simple: target × 3 minus the sum of flour temp, room temp, and friction (estimated 2–4°C for hand mixing, 5–8°C for stand mixers). Solve for water temp. The Recipe Lab does this in real time so you can stop guessing whether your kitchen is warm enough.
From the knowledge base.
Tested guides on fermentation, hydration, starters, and troubleshooting.
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Common questions.
How accurate is this schedule?
Treat it as a planning estimate, not a stopwatch. Real fermentation depends on starter strength, flour protein content, dough actual temperature (often warmer than ambient), and humidity. Use the schedule to plan your day, then judge bulk by visual cues: 50–75% rise, jiggle, visible dome.
Why is bulk longer at lower temperatures?
Yeast and bacterial enzymes work faster as temperature rises. The calculator uses a Q10 of roughly 2.2, so the fermentation rate increases about 2.2× for every 8°C — a touch more than a doubling. At 16°C bulk takes a bit over twice as long as at 24°C, with everything else equal.
What does "active and peaked" starter mean?
A peaked starter has at least doubled, shows a domed surface with visible bubbles, and floats in water. Use within an hour or two of peak. A recently fed starter still needs four to six hours to ripen. Cold starter from the fridge needs to warm up and feed before it's usable.
Can I skip the cold retard?
Yes. Set retard to zero and the calculator plans a same-day bake with final proof at room temperature, typically 1–2 hours after final shaping. You'll lose some flavor complexity but gain flexibility on baking day.
What's the difference between feed counts?
One feed works when your starter is already active or recently fed. Two feeds is the standard for a starter taken from the fridge — a refresh feed wakes it up, then a build feed produces the volume you need. Three feeds is for starters that have been stored more than a week and need extra revival cycles.
What hydration should I start with?
For your first ten loaves stay around 70–75% with bread flour. Higher hydration (80%+) demands stronger flour and better technique. Whole wheat absorbs more — bump hydration 5–8% if you're adding 20%+ whole grain. The Recipe Lab updates grams live so you can see the shift.
How does Live Bake mode work?
Generate a schedule, then click "Start Bake". The Live tab tracks elapsed time, shows your current step with a countdown, and previews what's next. The browser tab title flashes when a step is due so you don't miss a fold while doing something else. Everything is saved locally — no account, no server.
How do I know when bulk fermentation is done?
Watch the dough, not the clock: a 50–75% rise, a domed top, a few surface bubbles, and a slow jiggle. The calculator's time is there to plan around — these visual cues are the real signal. Pull it when it's puffy but still holds its shape; underproofed dough bakes dense and gummy.
Why does my bread overproof?
Usually because the dough was warmer than you assumed. Mixing friction leaves dough 1–3°C above room temperature, so a "6-hour" bulk in a 24°C kitchen can be done in four. Measure dough temperature, not air, and treat the bulk estimate as a ceiling, not a target.
Can I pause or shift the schedule partway through?
Yes — the easiest pause is a cold retard: once shaped, the loaf can sit in the fridge (~4°C) for 12–36 hours and bake when it suits you. To slow bulk, move the dough somewhere cooler; to speed it up, somewhere warmer, then re-run the calculator with the new temperature.
What flour should I use?
For your first loaves a strong bread flour (12–13% protein) is the most forgiving. All-purpose works but holds less gas. Whole wheat and rye ferment faster and absorb more water — add 5–8% hydration and expect a denser crumb. The Recipe Lab handles blends and shows true total hydration.
How do whole wheat and rye change the timing?
Both ferment noticeably faster than white flour — more enzymes and wild yeast in the bran and germ — so shorten the bulk and watch the dough closely; whole-grain doughs overproof in a blink. Start by cutting 20–30 minutes off the suggested bulk and adjust from what you see.