Starter Feeding Calculator
Enter your current starter amount and desired feeding ratio to calculate flour and water quantities. Adjust the temperature to estimate time to peak activity.
Feeding Ratio Quick Reference
Approximate time to peak activity for common feeding ratios at various temperatures. Times assume a mature, healthy starter.
| Ratio | 65°F / 18°C | 72°F / 22°C | 78°F / 26°C | 85°F / 29°C |
|---|---|---|---|---|
| 1:1:1 | 6-8 hrs | 4-6 hrs | 3-4 hrs | 2-3 hrs |
| 1:2:2 | 8-12 hrs | 6-8 hrs | 4-6 hrs | 3-4 hrs |
| 1:3:3 | 10-14 hrs | 8-10 hrs | 5-7 hrs | 4-5 hrs |
| 1:5:5 | 14-18 hrs | 10-14 hrs | 8-10 hrs | 6-8 hrs |
| 1:10:10 | 20-28 hrs | 16-22 hrs | 12-16 hrs | 10-14 hrs |
The Complete Guide to Sourdough Starter Maintenance
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 is what gives sourdough bread its distinctive tang, open crumb structure, 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 you produce.
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 a total of 150 grams. This standard ratio produces a predictable fermentation 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 existing culture must colonize a much larger quantity of fresh food. This is extremely useful for overnight builds: feed your starter at 10 PM with a 1:5:5 ratio at 68 degrees Fahrenheit, and it will peak around 8 to 10 AM the next morning, ready for you to mix your dough. The ratio acts as a time-control mechanism, giving you the ability to schedule your baking around your life rather than the other way around.
Conversely, lower ratios like 2:1:1 — retaining more starter than you add food — produce very fast peaks of 2 to 3 hours. This is sometimes useful when you need a quick turnaround, but the resulting starter tends to be more acidic and less vigorous because the culture runs out of food quickly and spends more time in a depleted state.
Flour Choice and Fermentation Speed
The type of flour you feed your starter has a measurable impact on fermentation speed, flavor development, and culture health. Whole grain flours — particularly whole rye and whole wheat — contain the bran and germ, which provide significantly more minerals, enzymes, and microbial nutrients than refined white flour. A starter fed with whole rye flour will typically peak 30 to 40 percent faster than the same starter fed with all-purpose white flour.
Many experienced bakers maintain their starter with a blend of flours to balance vigor with predictability. A 50/50 mix of all-purpose and whole wheat is a popular choice: the whole wheat component provides nutritional support for the culture while the all-purpose component moderates the fermentation speed for easier scheduling. Some bakers keep a small rye-fed starter for maximum vigor and build a levain with bread flour for their actual dough, getting the best of both worlds.
Protein content also matters. Bread flour with 11 to 13 percent protein produces a stronger gluten network in the starter, which traps gas more efficiently and gives you a more dramatic rise. All-purpose flour at 9 to 11 percent protein creates a thinner, more pourable starter at the same hydration. Neither is inherently better — it depends on your recipe and preferences.
Temperature: The Timeline Controller
Temperature is the most powerful variable controlling your starter's activity cycle. At 72 degrees Fahrenheit (22 degrees Celsius), a standard room temperature in many homes, a 1:1:1 feeding typically peaks in 4 to 6 hours. Increase the temperature to 82 degrees Fahrenheit (28 degrees Celsius) and that same feeding peaks in 2.5 to 3.5 hours. Drop to 62 degrees Fahrenheit (17 degrees Celsius) and peak extends to 8 to 12 hours.
This relationship follows an approximately exponential curve based on microbial metabolism rates. For every 15 degrees Fahrenheit increase within the viable range of 55 to 95 degrees Fahrenheit, fermentation speed roughly doubles. Smart bakers use this to their advantage: placing the starter in a warm oven with the light on, on top of the refrigerator, or in a proofing box to accelerate activity, or in a cool basement or wine fridge to slow it down.
The viable range for sourdough cultures is approximately 40 to 95 degrees Fahrenheit (4 to 35 degrees Celsius). Below 40 degrees, activity becomes negligible — this is the principle behind refrigerator storage. Above 95 degrees, you risk killing the yeast population, leaving only the more heat-tolerant bacteria, which produces an excessively sour, flat starter.
Hydration and Starter Consistency
Starter hydration — the ratio of water to flour by weight — affects both fermentation dynamics and handling properties. A 100 percent hydration starter (equal parts flour and water) is the most common and produces a thick, pancake-batter consistency. This is the standard assumed by most recipes and feeding calculators, including this one. It ferments at a moderate rate and is easy to measure and incorporate into dough.
Stiff starters at 50 to 65 percent hydration ferment more slowly, favor acetic acid production (vinegary tang), and are traditional in Italian baking for panettone and colomba. Liquid starters at 125 to 150 percent hydration ferment faster, favor lactic acid production (milder, yogurty tang), and are easier to pour and measure. Adjusting hydration gives you another tool for controlling both timing and flavor profile.
Signs of a Healthy Starter
A well-maintained starter should double or triple in volume within the expected timeframe after feeding, have a pleasant yeasty-tangy aroma (not acetone or nail-polish remover), show a web of bubbles throughout when viewed from the side of a clear container, and pass the float test at peak activity. The surface should dome upward at peak and then gradually flatten and begin to sink as the culture exhausts its food supply. Hooch — a layer of dark liquid on top — indicates the starter is hungry and needs feeding, but is not harmful. Simply stir it back in or pour it off and feed as usual.
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 (also called a preferment or production starter) is a separate build made specifically for a bake, using a portion of your maintained starter as a seed. Many bakers take a small spoonful of their refrigerated starter, build a levain at the desired ratio and temperature to peak at the time they want to mix dough, and leave the mother culture undisturbed in the fridge. This approach minimizes waste, separates baking decisions from maintenance decisions, and lets you use different flours and hydrations for the levain without changing your mother culture.