Watercolor illustration of sourdough bread and baking tools

Sourdough Calculator

Plan your bake with recipe scaling, levain builds, and a temperature-adjusted fermentation schedule.

Last reviewed: March 2026 | Based on fermentation kinetics research

Recipe

g
%
%
%

Starter & Environment

g
g
%
Advanced starter & environment options
hrs
How long your starter takes to double at room temp. Leave blank for default.
°C
If using a proofing box. Leave blank to use kitchen temp.
°C
75.2 °F
Desired Dough Temperature (DDT)
°F
°F
Required Water Temperature

Schedule

hrs

Recipe

Total Flour
514 g
Total Water
386 g
Levain
103 g
Salt
10 g
Effective Hydration
75.0%

Levain Build Plan

Build Summary
Stage Seed (g) Flour (g) Water (g) Total (g) Duration

Baking Schedule

Start
Ready to Eat
Time Step Duration Notes

How to Use This Sourdough Calculator

  1. Set your recipe — enter the dough weight per loaf, number of loaves, and hydration percentage. The default 75% hydration works well for most sourdough breads.
  2. Choose your flour — different flours ferment at different speeds. Whole wheat and rye ferment faster than white bread flour due to higher enzymatic activity and mineral content.
  3. Configure your starter — tell the calculator how much starter you have, its current state, and how much you want to keep for next time. The calculator will plan a levain build to match your needs.
  4. Set the temperature — your kitchen temperature is the single most important variable for fermentation timing. Use a thermometer for accuracy.
  5. Choose your schedule — "Start Now" calculates your timeline from the current moment. "Bread Ready By" works backwards from your target time to tell you when to begin.

Understanding Sourdough Fermentation Timing

Sourdough fermentation is governed by biological processes that respond to temperature following the Q10 rule: for every 10°C (18°F) increase in temperature, the fermentation rate approximately doubles. This means a dough at 28°C will ferment roughly twice as fast as the same dough at 18°C.

This calculator uses temperature-adjusted kinetics calibrated against published fermentation research. The base model assumes a 6-hour time-to-peak at 24°C with a standard 1:5:5 feeding ratio on white bread flour. From this baseline, the timing is adjusted for your specific temperature, flour type, inoculation ratio, and starter condition.

The inoculation percentage controls how much active culture is seeding your dough. Higher inoculation (25-30%) means more microorganisms competing for the same food supply — they reach peak activity faster, but with less complex flavor development. Lower inoculation (10-15%) gives a longer, slower fermentation with more organic acid production and deeper sour notes.

Baker's Percentages Explained

In baker's math, all ingredients are expressed as a percentage of the total flour weight. Flour is always 100%. If you have 500g of flour and 75% hydration, you need 375g of water. The levain (inoculation) percentage follows the same convention — 20% inoculation on 500g of flour means 100g of levain. This system makes it easy to scale recipes up or down while maintaining consistent ratios.

The Levain Build Process

Your levain is a portion of active starter mixed with fresh flour and water to build up enough volume for your recipe. The feeding ratio (e.g., 1:5:5 = 1 part starter : 5 parts flour : 5 parts water) determines how long it takes to reach peak activity. If you have very little starter, this calculator automatically plans a multi-stage build — first growing a small amount to an intermediate volume, then feeding again to reach the final target.

Tips for Consistent Results

Measure temperature accurately. A $10 kitchen thermometer eliminates the biggest source of timing error. Check both your kitchen ambient temperature and your water temperature before mixing.

Use the cold retard. An overnight fridge proof after shaping gives you scheduling flexibility and improves flavor. Shape in the evening, refrigerate, and bake straight from the fridge the next morning.

Watch the dough, not the clock. This calculator provides estimated timing with uncertainty windows (±15%). Your dough may be ready earlier or later depending on factors like humidity, water mineral content, and your starter's unique microbial culture. Look for 30-50% volume increase during bulk fermentation.

Frequently Asked Questions

Bulk fermentation typically takes 3-6 hours at room temperature (21-24°C / 70-75°F). The duration depends on kitchen temperature, inoculation percentage, flour type, and starter strength. Higher temperatures and more active starters shorten the time. This calculator adjusts timing using the Q10 temperature coefficient — fermentation rate roughly doubles for every 10°C increase.
Inoculation percentage is the amount of levain (active starter) used relative to the total flour weight in your dough. A 20% inoculation means using 20g of levain for every 100g of flour. Higher inoculation (25-30%) speeds up fermentation, while lower inoculation (10-15%) slows it down and develops more complex sour flavor.
Look for a 30-50% increase in volume, a domed surface with small bubbles, and a jiggly, airy texture when you gently shake the container. The dough should feel lighter and more airy than when you started. Under-fermented dough will be dense and tight; over-fermented dough will be slack, sticky, and may smell overly acidic.
A cold retard is an overnight (8-16 hour) refrigerated proof after shaping. It serves two purposes: scheduling flexibility (shape in the evening, bake in the morning) and flavor development. The cold temperature slows yeast activity while lactic acid bacteria continue producing organic acids, resulting in a more complex, tangy flavor and better oven spring.
Temperature is the single biggest factor controlling fermentation speed. Using the Q10 rule, fermentation rate roughly doubles for every 10°C (18°F) increase. At 18°C (64°F), bulk fermentation might take 8+ hours. At 28°C (82°F), it could finish in under 3 hours. The ideal range for most bakers is 24-26°C (75-79°F), balancing reasonable timing with good flavor development.
For beginners, start with 70% hydration for easier handling. Standard country sourdough uses 72-78%. For open crumb and ciabatta, try 78-85%. Above 85% is advanced territory. Higher hydration makes dough stickier but produces a more open, airy crumb.
Use the DDT (Desired Dough Temperature) formula: Water Temperature = (DDT x 3) - Room Temperature - Flour Temperature - Friction Factor. The standard DDT for sourdough is 78°F (25.5°C). Friction factor is 20°F for hand mixing, 30-40°F for stand mixers. This calculator computes it automatically in the DDT section.
Yes, all-purpose flour works well for sourdough. It has slightly less protein than bread flour (10-12% vs 12-14%), producing a softer crumb with less chew. Many bakers blend AP with bread flour or whole wheat for the best of both worlds.