Sourdough Starter Calculator

Your levain is at peak activity when it has at least doubled in volume, shows a domed top (not yet deflated), has bubbles throughout, and passes the float test — drop a small spoonful in water; if it floats, the levain is well-aerated and ready. A ripe levain will also smell pleasantly tangy and yeasty.

A very high inoculation rate causes rapid fermentation that can quickly become over-ripe. An over-fermented levain loses its leavening power and may impart harsh, very sour flavors. If your levain peaks too quickly, refrigerate it briefly to slow fermentation until you're ready to mix your dough.

Technically yes, but discard starter is unfed and has consumed most of its food supply. A levain built from discard may ferment slowly, unevenly, or lack vigor. For best results, build your levain from recently fed, active starter at peak or just before peak activity.

Fermentation rate roughly doubles with every 18°F (10°C) increase in temperature. A levain that ripens in 8 hours at 68°F will ripen in about 4 hours at 78°F. Cooler temperatures slow activity; warmer temperatures accelerate it. Adjust inoculation rate or ambient temperature to control timing.

Most starters are fed with white bread flour or all-purpose flour, which provides consistent fermentation. Adding 10-20% whole wheat or rye flour to feedings increases microbial activity because these flours contain more minerals and wild yeast naturally present in the bran. Rye flour in particular is highly stimulating for starter activity.

At room temperature, a starter should be fed once or twice daily. If refrigerated, weekly feeding is sufficient. Before baking, bring the refrigerated starter to room temperature and give it 1-2 feeds at room temperature to ensure it is active and vigorous before building your levain.

Feeding ratios express starter:flour:water by weight. A 1:5:5 ratio means for every 1g of starter, you add 5g flour and 5g water. This dilutes the acid load, resulting in a less sour starter. A 1:2:2 ratio is a more frequent, less diluted feed used to maintain high activity. Higher ratios extend the time to peak.

An acetone-like smell indicates your starter is very hungry and has run out of food, producing ethyl acetate instead of lactic and acetic acids. Feed it immediately and more frequently. A healthy starter should smell pleasantly sour, yogurt-like, and mildly yeasty — not harsh or chemical.

Yes. Rye levains are common in German and Scandinavian baking. Whole grain levains ferment faster due to higher enzyme activity and provide a more complex, earthy flavor. They typically require shorter build times and may need slightly more water since whole grain flours absorb more liquid.