Free sourdough calculator using Baker's Math. Calculate flour, water, starter & salt ratios instantly. Includes a bulk fermentation timer, sourdough temperature chart, and starter feed calculator — all in real time.
Enter flour weight — every other ingredient is calculated automatically using Baker's Math
Calculate exactly how much flour and water your starter needs at each feeding
Build your pre-ferment precisely — calculate seed, flour, and water for your levain
Find the right water percentage for your skill level and bread style
| Hydration | Level | Dough Feel | Crumb Style | Best For |
|---|---|---|---|---|
| 50–59% | Beginner | Firm, easy to knead, non-sticky | Tight, dense crumb | Bagels, flatbreads, stiff starter builds |
| 60–69% | Beginner | Smooth, slightly tacky surface | Soft with even structure | Sandwich loaf, pan bread, tin loaf |
| 70–74% | Beg–Mid | Tacky, manageable with wet hands | Open crumb, good oven spring | Classic country boule — ideal starting point |
| 75–80% | Intermediate | Sticky — use stretch & fold technique | Open, irregular crumb | Artisan boule, bâtard, batard |
| 81–89% | Advanced | Very sticky — always use wet hands | Very open, large irregular holes | High hydration sourdough, ciabatta-style |
| 90%+ | Expert | Slack, almost pourable | Extremely open, glossy crumb | Focaccia, experimental high-hydration bakes |
Bulk fermentation time changes dramatically with kitchen temperature. Use this sourdough temperature chart with 20% starter as your baseline — then adjust with the fermentation timer above.
| Kitchen Temp | Condition | Bulk Ferment (20% starter) | Starter % Adjustment | Notes |
|---|---|---|---|---|
| 16–18°C / 61–64°F | Very Cool | 10–14 hours | Increase to 25–30% | Cold garage or winter kitchen — slow and deeply flavorful |
| 19–21°C / 66–70°F | Cool | 7–10 hours | Increase to 22–25% | Typical UK or autumn kitchen — relaxed sourdough schedule |
| 22–24°C / 72–75°F | Ideal | 4–6 hours | Standard 18–20% | Optimal range — balanced flavor and manageable sourdough timeline |
| 25–27°C / 77–81°F | Warm | 3–4 hours | Reduce to 12–15% | Warm summer kitchen — monitor closely, proofing sourdough faster |
| 28–30°C / 82–86°F | Hot | 2–3 hours | Reduce to 8–12% | Risk of over fermented sourdough — check every 30–45 minutes |
Proofing sourdough in the refrigerator after shaping gives you better flavor, easier scoring, and a flexible sourdough schedule.
| Proof Method | Temperature | Duration | Flavor Profile | Best For |
|---|---|---|---|---|
| Room temp proof | 22–24°C / 72–75°F | 2–4 hours | Mild, yeasty | Same day sourdough — bake the same evening |
| Cold proof (fridge) | 2–5°C / 36–41°F | 8–16 hours overnight | Complex, tangy sour | Classic artisan loaf — mix today, bake tomorrow |
| Extended cold proof | 2–5°C / 36–41°F | 16–36 hours | Bold, pronounced sour | Deep flavor development — sourdough batard or boule |
All times assume an active, well-fed starter. Use the bulk fermentation timer above for a personalized estimate based on your kitchen temperature and starter percentage.
Small adjustments that make a measurable difference in the final loaf
Dough ferments roughly twice as fast for every 5°C rise in temperature. Use less starter in a warm summer kitchen, more in a cold winter one. Refer to the sourdough temperature chart above for your kitchen's expected bulk fermentation window, and adjust your sourdough schedule accordingly.
A cup of flour can vary by 50g depending on how it's scooped. A digital scale is the most impactful investment any sourdough baker can make — accuracy is repeatability. Use our sourdough starter calculator and recipe calculator in grams for the most consistent results.
Begin at 68–72% hydration. Master the feel of a manageable dough before pushing into high hydration sourdough territory. Each 2–3% increase requires noticeably different handling technique — don't rush the progression. A sourdough batard or artisan boule at 75% is a great intermediate goal.
Drop a small spoonful of fed starter into water. A float means it's full of gas and ready to leaven your bread. If it sinks, give it more time — using weak starter is the most common beginner mistake and the leading cause of dense, underproofed sourdough with poor oven spring.
Mix flour and water, then rest 30–60 minutes before adding starter and salt. This autolyse sourdough step develops gluten naturally, giving you a stronger, more extensible dough without extra kneading. Skip autolyse only if you're making same day sourdough and pressed for time.
After shaping, cold proof sourdough overnight in the refrigerator (8–16 hours). Slower fermentation at low temperatures produces more lactic and acetic acids — the complex sour flavor that makes sourdough distinctive. Cold proofing also makes scoring easier and gives you a flexible baking schedule.
Baker's Math (also called Baker's Percentages) is the professional standard for writing and comparing bread recipes. Every ingredient is expressed as a percentage of total flour weight, which is always defined as 100%. Water, starter, salt, and any additions are all percentages of that flour base.
The power of Baker's Math is in scaling. A recipe that calls for 70% water will produce the same results whether you bake 300g or 3kg of dough — just multiply each percentage by the flour weight. There's no mental arithmetic in the kitchen; the ratios do the work.
Our sourdough calculator applies Baker's Math automatically. Enter your flour weight, adjust the hydration and starter sliders, and every other ingredient weight appears instantly in real time — in both grams and ounces.
Start by selecting a loaf size preset (300g to 1.5kg) or entering your own flour weight. Set your water percentage using the hydration slider — 70% is the best starting point for most bakers. Set starter to 15–20% and salt to 2%, and your full ingredient list updates live. The True Hydration figure accounts for the water already inside your starter, giving you the actual hydration of the finished dough. The bulk fermentation timer at the bottom adjusts automatically as you change your starter percentage and kitchen temperature.
Bulk fermentation sourdough is the period after mixing when the dough ferments as a single mass before shaping. It's the most important — and most misunderstood — stage in sourdough baking. Rather than watching the clock, watch the dough: you're looking for a 50–75% volume increase, visible bubbles on the surface and sides of the container, and a dough that feels lighter and jiggles slightly when you shake the container.
Over fermented sourdough feels slack, sticky, and smells sharply of alcohol. It will spread flat rather than holding its shape when tipped out. Underproofed sourdough is dense with a tight crumb and will often have a large hollow near the top of the loaf. The sourdough temperature chart on this page shows how bulk fermentation time changes with your kitchen temperature — use it alongside the fermentation timer in the calculator.
The calculator supports both grams and ounces. Toggle between units at the top of the recipe calculator and all values update instantly. We strongly recommend working in grams — the metric system gives finer precision and makes it easier to scale recipes correctly.
Hydration is the ratio of total water to total flour by weight, expressed as a percentage. It's the single most influential variable in sourdough baking. Hydration determines how the dough handles, how it rises, and what the interior (crumb) looks like when you slice the loaf.
Lower hydration (60–70%): The dough is firm and easy to shape. Forgiving for beginners. Produces a tighter crumb — still delicious, with a defined structure that holds sandwich fillings well. Great for your first ten loaves.
Medium hydration (70–80%): The sweet spot for most artisan loaves. The dough is sticky but manageable using the stretch-and-fold technique. Produces an open, irregular crumb with a crisp, crackly crust. This is the range most home sourdough bakers work in — including for a sourdough batard or classic boule.
High hydration sourdough (80%+): Rewarding but demanding. The dough is very slack and requires confident technique. Results in a highly open crumb with a thin, shattering crust. Requires well-developed gluten and precise fermentation timing — the sourdough temperature chart becomes especially critical at these hydrations.
After bulk fermentation and shaping, you have two proofing options. Room temperature proofing takes 2–4 hours and suits same day sourdough — mix, bulk, shape, proof, and bake all in one day. Cold proof sourdough overnight in the refrigerator takes 8–16 hours at 2–5°C and produces significantly more complex flavor, as the slow fermentation at low temperature encourages acetic acid production. Cold proofed loaves also hold their shape better, making scoring easier. If you're asking how long to proof sourdough, the answer depends almost entirely on your chosen sourdough schedule — see the proofing guide table above.
Starter ratios describe the proportion of old starter to new flour and water. A 1:2:2 ratio means 1 part starter, 2 parts flour, 2 parts water (all by weight). Higher ratios like 1:5:5 or 1:10:10 dilute the culture more heavily, extending the time before it peaks — ideal for overnight timings. The Starter Feed Calculator eliminates guesswork by computing exact amounts from your chosen ratio.
For flour, bread flour (12–14% protein) gives the best results. Many bakers blend in 10–20% whole wheat sourdough starter flour or rye to add nutrients and more complex flavor. A rye sourdough starter is particularly active and can help strengthen a sluggish culture. Avoid cake flour, self-raising flour, or highly bleached flour, as these inhibit fermentation.
Everything you need to know about sourdough ratios, Baker's Math, bulk fermentation, and this calculator
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