Sourdough Calculator
Calculate sourdough bread ratios for flour, water, starter and salt by target dough weight and hydration percentage
Recipe
Total: 1000g dough
Fermentation Time
At 20°C
12 hours
Bulk fermentation until dough has increased by 30-50% and shows signs of strength
Sourdough by Baker's Percentage
Sourdough recipes work in baker's percentages, where flour is always 100% and everything else is expressed as a percentage of the flour weight. Standard hydration runs 75 to 80% (so 750-800g water per 1kg flour), starter is typically 20% (200g starter per 1kg flour), and salt is locked at 2% (20g per 1kg flour). The calculator inverts this: tell it the target finished dough weight, and it back-calculates flour, water, starter and salt to hit that total.
For a single 1kg loaf at 75% hydration with 20% starter, that means roughly 510g flour, 383g water, 102g starter and 10g salt. Increase hydration to 80% for a more open, airy crumb (the trade-off is a stickier, harder-to-shape dough). Drop to 70% for a tighter, more sandwich-bread crumb that's easier for first-time bakers to handle. The 75% default is the proven middle ground.
Fermentation Time and Why Temperature Matters
Bulk fermentation is where sourdough becomes sourdough - the wild yeast and bacteria in the starter ferment the flour, producing the characteristic flavour, structure and tang. Time depends almost entirely on dough temperature. The calculator estimates 18 hours at 15°C, 12 hours at 18 to 22°C, 8 hours at 22 to 25°C, and 6 hours above 25°C. These are bulk times to roughly 30 to 50% volume increase, not until "doubled" which is too long for most flour types.
Don't trust the clock alone - read the dough. Signs of correctly bulked dough: 30 to 50% volume increase, jiggly when you shake the bowl, dome shape with visible bubbles on the surface, and a slight wine-like aroma. Under-fermented dough is dense and gummy. Over-fermented dough collapses, smells acetic (vinegar-like), and bakes flat. Day three of starter feeding produces the most active culture; for pizza dough or other lower-hydration breads see the [Pizza Dough Calculator](/pizza-dough-calculator).
Hydration Effects on Final Loaf
| Hydration | Crumb Style | Difficulty | Best For |
|---|---|---|---|
| 65-70% | Tight, sandwich | Easy | Beginners, sandwich loaves |
| 75% (default) | Open, balanced | Moderate | Standard country loaf |
| 80% | Very open | Hard | Boules with big holes |
| 85%+ | Custard-like | Expert | Ciabatta, focaccia |
Frequently Asked Questions
How active does my starter need to be?
Use a starter that has doubled in volume within 4 to 6 hours of feeding. The float test (drop a teaspoon in water, it should float) is a useful cross-check. A sluggish starter means a slower bulk and a flatter loaf. Feed at a 1:5:5 ratio (10g starter, 50g flour, 50g water) the night before a bake for a vigorous, gas-producing rise.
Why is my sourdough so dense?
Almost always under-fermentation. Watch for the 30 to 50% volume increase rather than relying on the clock. Cold kitchens (under 18°C) extend bulk to 14 to 18 hours, far longer than most recipes suggest. Other causes: weak starter, salt added too early (it slows yeast), or shaping that knocked all the gas out before the final proof.
Can I use plain flour instead of strong bread flour?
Plain flour produces a denser, less open loaf because of its lower protein (around 9 to 10%) compared to strong bread flour (12 to 14%). For sourdough, you want the higher protein for the gluten development that holds air through the long ferment. Use plain flour if it's all you have, but expect a tighter crumb.
How long does fresh sourdough keep?
Three to four days at room temperature in a paper bag (cut-side down on a board), or freeze sliced for up to three months. Don't store in plastic - the crust softens. A stale day-three loaf revives with a 5-minute blast in a 200°C oven, restoring the crust crackle and warming the crumb.