How long should bulk fermentation take? It depends — on dough temperature above all, but also on how much starter you added, your hydration, your salt, and whether the dough is headed for the fridge. This calculator runs Sourjoe’s calibrated fermentation model to turn those inputs into a concrete estimate: bulk rise, proof, and total rise time.
It handles the cases most timing charts ignore: mix-method drift, dough-mass cooling, shape-and-chill retards, and how sour you want the final loaf (the Tang setting trades fridge time for acidity). Treat the numbers as the center of a forgiving window, not a stopwatch — your dough gets the final vote.
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Rise Time Calculator
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Opened from the Bread Recipe Supercalculator: dough temperature, inoculation, hydration, salt, dough mass (the recipe’s total weight) and room temperature (from the Book of Sourjoe Settings) are being supplied, and are highlighted in green below. The estimate is the same one the Supercalculator shows. Open this calculator from the Calculator List to enter your own figures.
? Estimate bulk rise, proof, and total rise time from dough temperature, inoculation, hydration, and salt.
Temperature Units:
Parameter
Value
? Initial Mix Method
? Autolyse Time
hours
? Room Temperature
? Proofing Method
? Auto Bulk Cut
? Bulk Completed
--
%
? Fridge Temperature
? Dough Mass
? Dough Temperature
? Inoculation
%
? Dough Hydration
%
? Salt
%
? Bulk Time
--
? Proof Time
--
? Total Rise Time
--
? TangMild (0)
? Tang Proof Time
--
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Rise Time Estimate
What This Estimator Does
It predicts bulk, proof, and total rise time from four levers — dough temperature, inoculation (how much leaven relative to flour), hydration, and salt — measured against a reference bake. It is a field model, not a law of nature: a tunable starting point you calibrate to your own starter and kitchen.
The Four Levers
Lever
Direction
Why
Temperature
Warmer → faster
The strongest lever. Rate roughly doubles per ~10°C (the Q10 factor).
Inoculation
More leaven → faster
More active culture means more fermentation power per gram of flour.
Hydration
Wetter → slightly faster
Mobility helps enzyme and microbial activity, modestly.
Salt
More salt → slower
Salt restrains yeast and tightens gluten, damping the pace.
Initial Mix Method
The bulk clock is a fermentation clock — it starts when the leaven goes in. Under Fermentolyse that is the initial mix. Under Autolyse the flour and water rest first with no fermentation, so the autolyse rest is added to the total timeline, and during that rest the dough temperature drifts toward room temperature (an exponential relaxation with the tunable time constant below) — bulk and proof then run at the drifted temperature, not the mix temperature. The optional rate bonus (default 0 = off) lets you model the mild fermentation acceleration a completed autolyse gives via enzyme activity, if your bakes show it.
Proofing Method — the Fridge Retard
Under Ambient the proof runs at the ferment temperature, as it always has. Under Retard the shaped dough goes into the fridge at the end of bulk, and two things happen at once: the dough cools toward the fridge temperature (Newton cooling — a bigger dough mass cools more slowly, scaling with mass2/3, the surface-to-volume law), and it keeps fermenting at whatever rate its current temperature allows. The model treats proof as an accumulated fermentation dose: the ambient proof time is re-expressed as a required dose, and the dough banks that dose minute by minute along the cooling curve — quickly while still warm, then very slowly once cold.
Below the Cold Knee (default 20 °C — the reference temperature itself) a much steeper cold-side Q10 takes over (default 15), because dough fermentation collapses far faster on the way into the fridge than a straight Q10 of 2 predicts: the outer dough chills long before the core probe does, and sourdough cultures slow disproportionately as they cool. Calibrated against instrumented live retards (Sep 2026), the practical picture is that the descent into the fridge delivers nearly the whole proof dose and the cold hold then acts as a clamp — hours at fridge temperature add almost no further rise. That clamp is why a retard is so forgiving, and why 12-hour and 18-hour holds of the same dough bake up so similarly: near the ready point the dough is banking dose so slowly that the same 10% over-proof margin that passes in minutes at room temperature takes many hours in the fridge. For practical scheduling the fridge leg is capped at 24 hours (the Practical Proof Cap below): theoretically a very cold retard can point far past that — the result note reports the full-proof point honestly — but hardly a recipe in print proofs beyond 24 hours, so the plan you see never does either. Cold readiness is judged at the poke standard — retarded dough is deliberately baked slightly under the ambient full-proof bar (the Cold Readiness Fraction below, default 0.85, measured on instrumented twin loaves) — and the calculator reports both that ready time and the edge of the forgiving window (110% of it). If the dose does not complete within 72 hours, your fridge is cold enough to effectively hold the dough, and the calculator says so rather than inventing a number.
Shape-and-Chill — the Book Method
Most published overnight methods do not retard a fully bulked dough — they shorten bulk on purpose, shape, and refrigerate, letting the remaining bulk and the whole proof finish slowly in the cold. That is what the 8–16 hour figures in the bread books really are: a deliberately under-proofed entry plus a wide fridge window plus flavour time. Shape-and-Chill models it directly: tell the calculator how far bulk had come when you shaped (Bulk Completed %, most books land around 70–85%), and the unbanked remainder of the bulk dose rides into the fridge on top of the proof dose. At 100% it is Retard exactly.
The Tang Slider
Rise and tang run on different clocks. The gas that proofs the loaf comes mostly from the yeasts, whose activity collapses in the cold; the acids that make it tangy come mostly from the bacteria, whose activity falls off far more gently. So fridge hours past the structural ready point add almost no rise but keep adding tang — which is the entire flavour argument for the long retard. The Tang slider turns that into a bake time: it is modeled as a second dose (the acid dose, with its own gentler Q10 pair below) integrated along the same cooling curve. Mild means bake at the structural ready point; higher settings ask for a multiple of the ready-point acid (up to ×2.5 at Very Tangy, tunable below) and are answered with a later recommended fridge time. The scale is deliberately relative — an absolute sourness scale would demand calibration nobody has — and a very tangy target can land past the forgiving window, in which case the calculator says so and names the trade: a slacker, more delicate dough, or a colder fridge.
The Model
FermentTempC = RoomTempC + (DoughTempC − RoomTempC) × e^(−AutolyseHours ÷ DriftTimeConstant)
(Autolyse only; under Fermentolyse, FermentTempC = DoughTempC)
AutolyseBoost = 1 + BoostPerHour × AutolyseHours
TemperatureRate = Q10 ^ ((FermentTempC − RefTempC) / 10)
InoculationRate = (Inoc / RefInoc) ^ InocExponent
SaltRate = 1 − SaltCoeff × (Salt − RefSalt)
HydrationRate = 1 + HydrationCoeff × (Hyd − RefHyd)
BulkHours = RefBulkHours ÷ (TempRate × BulkInocRate × SaltRate × HydrationRate × AutolyseBoost)
ProofHours = RefProofHours ÷ (TempRate × ProofInocRate × SaltRate × HydrationRate × AutolyseBoost)
Retard (fridge proof) only:
τ = RetardTimeConstant × (DoughMass ÷ 1000 g)^(2/3)
DoughTemp(t) = FridgeTempC + (FermentTempC − FridgeTempC) × e^(−t ÷ τ)
Rate(T) = Q10^((T − RefTempC)/10) for T ≥ ColdKneeC
= max( ColdFloorRate, Q10^((ColdKneeC − RefTempC)/10) × ColdQ10^((T − ColdKneeC)/10) ) for T < ColdKneeC
(the deep-cold "trudge" floor: real dough never quite stops — default 0.04
of reference speed, desk-calibrated on the TPL cold anchors + live bakes)
(default ColdKneeC = RefTempC = 20 °C, so the first factor is 1 and the fridge
descent runs on the single steeper ColdQ10 curve below reference)
ProofDose = RefProofHours ÷ (ProofInocRate × SaltRate × HydrationRate × AutolyseBoost)
ColdTarget = ProofDose × ColdReadyFrac
(cold dough is baked at poke-ready — slightly under the ambient full-proof
standard, by design; default 0.85, measured on twin live loaves Sep 2026)
ProofHours = the time t at which ∫ Rate(DoughTemp) dt reaches ColdTarget
(forgiving window ends when the integral reaches 110% of ColdTarget)
Shape-and-Chill only:
BulkHours = full-bulk hours × BulkCompleted%
FridgeDose = (1 − BulkCompleted%) × BulkDose + ProofDose
Tang (cold methods, slider > Mild):
AcidRate(T) = AcidQ10^((T − RefTempC)/10) for T ≥ 10 °C
= AcidQ10^((10 − RefTempC)/10) × AcidColdQ10^((T − 10)/10) for T < 10 °C
TangTarget = (1 + slider × (TangMax − 1)) × acid banked at the ready point
TangProofTime = the fridge time t at which ∫ AcidRate(DoughTemp) dt reaches TangTarget
TotalHours = AutolyseHours + BulkHours + ProofHours
Every constant is exposed below so you can tune the model to your bakes without it being a black box. The default reference point is 20°C, 20% inoculation, 65% hydration, 2% salt.
Model caution: this is not a fermentation law. Starter strength, flour mix, dough handling, and your chosen "done" point all move the real times. Calibrate against your own bakes.
Now you know how long — want to know when? The Sourdough Schedule Builder turns these same numbers into a start-to-finish timeline: mix, fold, shape, proof and bake, each on the clock, so nothing lands at 3 a.m.
Rise Time Calculator FAQ
How long should bulk fermentation take?
At typical room temperatures with a 20% inoculation, expect 3–5 hours — but the honest answer is “it depends on dough temperature more than anything else,” which is exactly what this calculator models. A couple of degrees warmer can shave an hour; a cool kitchen can add two.
What affects sourdough rise time the most?
Dough temperature, by a wide margin, then inoculation percentage (how much leaven), then hydration and salt. That's why the inputs above lead with temperature — and why serious bakers control it with the DDT method rather than hoping.
Does salt slow down fermentation?
Yes, measurably — salt is hygroscopic and competes with the microbes for water, so a 2.5% dough ferments slower than a 1.8% one. The model accounts for it, which is one reason its estimates beat rule-of-thumb charts.
How does a cold retard change the timing?
Refrigeration slows yeast to a crawl while cold-tolerant bacteria keep building acetic acid — so a 12–24 hour retard adds tang and scoring-friendly firmness while barely advancing the rise. Use the calculator's cold-retard and tang controls to plan it instead of guessing.
Want to know why this works? Every model and constant behind this calculator is explained, derived, and put to work in The Book of Sourjoe — the interactive book this calculator was built for.
