Sourdough Starter Feeding Calculator

The complete guide to sourdough starter maintenance

Ratios, hydration, flour, and temperature — the four levers that control your starter.

A sourdough starter is a living culture of wild yeast and lactic acid bacteria that you maintain through regular feedings of flour and water. This symbiotic colony gives sourdough bread its distinctive tang, open crumb, and superior keeping qualities compared to commercial yeast breads. Understanding how to feed and maintain your starter is the single most important skill in sourdough baking, because the health of your starter directly determines the quality of every loaf.

Understanding feeding ratios

The feeding ratio expresses the proportion of existing starter to fresh flour and water. A 1:1:1 ratio means equal parts by weight of starter, flour, and water. If you retain 50 grams of starter, you add 50 grams of flour and 50 grams of water for 150 grams total. This standard ratio produces a predictable cycle of about 4 to 6 hours at room temperature before the starter reaches its peak — the point of maximum yeast activity and gas production.

Higher ratios like 1:5:5 dramatically extend the time to peak because the small amount of culture must colonize a much larger quantity of fresh food. This is useful for overnight builds: feed at 10 PM with a 1:5:5 ratio at 68 degrees Fahrenheit and it will peak around 8 to 10 AM, ready to mix dough. The ratio acts as a time-control mechanism, letting you schedule baking around your life. Lower ratios like 2:1:1 produce very fast peaks of 2 to 3 hours but tend to be more acidic and less vigorous.

Flour choice and fermentation speed

The flour you feed your starter has a measurable impact on speed, flavor, and culture health. Whole grain flours — particularly whole rye and whole wheat — contain the bran and germ, which provide far more minerals, enzymes, and microbial nutrients than refined white flour. A starter fed with whole rye typically peaks 30 to 40 percent faster than the same starter fed with all-purpose. Many bakers maintain a 50/50 all-purpose and whole wheat blend to balance vigor with predictability. Protein content matters too: bread flour at 11 to 13 percent builds a stronger gluten network that traps gas efficiently, while all-purpose creates a thinner, more pourable starter at the same hydration.

Temperature: the timeline controller

Temperature is the most powerful variable controlling activity. At 72 degrees Fahrenheit (22 degrees Celsius), a 1:1:1 feeding typically peaks in 4 to 6 hours. At 82 degrees Fahrenheit (28 degrees Celsius) that same feeding peaks in 2.5 to 3.5 hours; at 62 degrees Fahrenheit (17 degrees Celsius) it extends to 8 to 12 hours. Roughly, for every 15 degrees Fahrenheit increase within the viable range of 55 to 95 degrees, fermentation speed doubles. Below 40 degrees activity becomes negligible — the principle behind refrigerator storage. Above 95 degrees you risk killing the yeast population, leaving a flat, overly sour starter.

Hydration and starter consistency

Starter hydration — the ratio of water to flour by weight — affects both fermentation dynamics and handling. A 100 percent hydration starter (equal flour and water) is the most common and gives a thick, pancake-batter consistency; this is the standard assumed by most recipes and by this calculator. Stiff starters at 50 to 65 percent hydration ferment more slowly and favor acetic (vinegary) tang, traditional in panettone. Liquid starters at 125 to 150 percent hydration ferment faster and favor milder, yogurty lactic tang. Adjusting hydration is another tool for controlling both timing and flavor.

Signs of a healthy starter

A well-maintained starter should double or triple in volume within the expected window, smell pleasantly yeasty-tangy (not like acetone), show a web of bubbles through the side of a clear jar, and pass the float test at peak. The surface domes at peak, then flattens and sinks as food runs out. Hooch — a dark liquid layer on top — means the starter is hungry, not spoiled; stir it in or pour it off and feed as usual. Use your starter at or just before peak for the strongest rise in your dough.

Building a levain vs. feeding your starter

There is an important distinction between routine maintenance feedings and building a levain for baking. Your maintenance starter is the mother culture you keep alive indefinitely. A levain (or preferment) is a separate build made for a specific bake, using a spoonful of your maintained starter as seed. Many bakers build a levain at the ratio and temperature needed to peak when they want to mix dough, leaving the mother culture undisturbed in the fridge. This minimizes waste and lets you use different flours and hydrations for the levain without changing your mother culture.