Sourdough Starter Calculator

The ratio you pick in this sourdough starter calculator is really a dial for timing and flavor, not a fixed rule. 1:1:1 is the fastest option: with proportionally more established starter relative to fresh flour and water, it ferments quickly, commonly peaking in around 4 to 6 hours at a warm room temperature, and tastes noticeably more sour because the culture spends less time diluted with fresh food. King Arthur Baking treats 1:1:1 as a practical minimum — enough fresh flour and water to keep the yeast and bacteria in a starter properly fed and in balance — which is also why it's the ratio used in King Arthur's own base starter recipe.

1:2:2 stretches that same fermentation out to roughly 6 to 8 hours. It's often described as the most generally useful everyday ratio because it comfortably bridges a feed-the-night-before, bake-in-the-morning schedule without needing the fridge, and it produces a milder, less aggressively sour result than 1:1:1 while still being ready well within a single day.

Move up to 1:5:5 and there's proportionally much less established starter diluted into a much larger amount of fresh flour and water, which slows everything down — peaking somewhere in the 10-to-14-hour range at room temperature. That slower pace suits an overnight levain build, a cooler kitchen, or a baker who wants a milder-tasting starter without switching flours. None of these three is objectively correct: the same starter can be fed at different ratios on different days depending purely on when you plan to bake and how sour you want the result, and this calculator's job is just to turn whichever ratio you pick into exact gram amounts instead of a guess.

The ratio isn't the only thing that shapes flavor and speed — flour choice interacts with it. A starter fed partly or entirely with whole wheat or rye flour ferments noticeably faster than one fed only white bread flour, because whole grains carry more of the wild yeast and bacteria (and more of the nutrients those organisms feed on) than refined flour does. That means a whole-grain starter at 1:2:2 can behave closer to a white-flour starter at 1:1:1, which is worth factoring in before assuming a slow starter is unhealthy rather than just fed a slower-fermenting flour.

The float test is the sign most beginners reach for first: drop a small spoonful of unstirred starter into a glass of room-temperature water, and if it floats, the theory goes, there's enough trapped gas for the starter to be considered active. It's a genuinely useful quick check, but it isn't the most reliable one on its own — it can give a false positive from a single large bubble, or a false negative in a stiffer, low-hydration starter that simply doesn't float even when it's perfectly capable of leavening bread. Treat it as one supporting data point, not a pass/fail test to bake or not bake around.

A more dependable sign is doubling time: how long it takes a freshly fed starter to double in volume. A healthy, well-established starter at a warm room temperature, roughly 70 to 75°F, typically doubles somewhere in the 4-to-8-hour range depending on the feeding ratio used, and the doubling should be repeatable — the same starter roughly doubling across three consecutive feedings in a row is a stronger signal than a single good rise, since one lucky bubble-heavy rise doesn't confirm the culture is consistently strong. Marking the starter's level on the jar with a rubber band or grease pencil right after feeding makes this easy to track visually without guesswork.

Beyond the numbers, look for visible bubbles distributed through the starter (not just on the surface), a domed rather than flat or sunken top, and a pleasant tangy-yeasty smell rather than a sharp acetone or alcohol note, which usually signals the starter has gone past peak and is hungry again.

A rubber band or a small aliquot jar — a separate straight-sided jar holding a spoonful of the same freshly fed starter — makes doubling easier to judge than eyeballing the main jar, since a wide or oddly shaped container can rise unevenly and make the true increase in volume hard to see. If a starter consistently fails to double even after several days of regular feeding, the more likely explanations are a feeding ratio that's diluting it faster than it can rebuild, a kitchen that's too cool, or a starter that's still young rather than a starter that's failed outright; very few starters, once established, are actually dead.

The same feeding ratio behaves differently depending on the room it's sitting in, because the yeast and bacteria in a starter are temperature-sensitive organisms, not a fixed chemical reaction. Cooler temperatures, below roughly 70°F (21°C), slow fermentation down noticeably; warmer temperatures in the 76-to-82°F (24-to-26°C) range speed it up. That's the same relationship that makes a 1:1:1 starter peak faster on a warm summer counter than it does in a chilly winter kitchen, even though the gram amounts this calculator returns don't change.

In a warm kitchen, a starter may need feeding twice a day just to avoid over-fermenting and running out of food between feeds, and some bakers deliberately reduce how much ripe starter they carry over into the next feeding — down to roughly 10 to 15%, versus a more typical 20 to 25% in cooler months — to slow the pace back down rather than switching ratios entirely. In a cool kitchen, warming the water used for feeding to around 80°F is a common way to compensate without moving the jar somewhere warmer.

At the opposite extreme, refrigeration between 45 and 55°F (7 to 13°C) can stretch the interval between feedings out to a week or more, which is why bakers who don't bake daily typically store their starter cold and pull it out to warm up and feed a day or two before they plan to bake, rather than maintaining it at room temperature year-round.

Temperature and ratio work together rather than separately, which is where this calculator's role stays consistent even as conditions change: the gram amounts for a given ratio and target weight don't shift with the weather, but how soon that starter peaks after mixing does. A baker in a cold apartment who wants a same-day 1:1:1 starter might feed with warm water and set the jar in a slightly warm spot (near a proofing oven light, for example), while the same ratio on a hot kitchen counter might peak and start to deflate before it's convenient to bake, which is a common reason a starter that "always worked" suddenly seems over-proofed or unusually sour once summer arrives.

"Discard" and "active starter" describe the same culture at two different points in its feeding cycle, and recipes are not interchangeable between them. Active starter is starter that's been recently fed and has risen close to or at its peak — bubbly, aromatic, and strong enough to leaven a bread dough on its own, which is what a recipe means when it calls for active starter in a loaf, dinner rolls, or pizza dough that relies on the starter as the sole leavening agent.

Discard is the portion removed and set aside before or after a feeding, rather than fed forward. On its own it has little to no reliable rising power left, but it still carries the starter's sour flavor and fermented character, which is exactly why it gets folded into pancakes, muffins, crackers, and other recipes that already get their lift from baking powder or baking soda rather than from the starter itself. Using discard in a recipe written for active starter typically produces a dense, underproofed result, because the recipe is counting on leavening power the discard no longer reliably has.

This calculator's output — the starter, flour, and water needed at whatever ratio you choose — describes a normal feeding, not a discard recipe. If you're deliberately keeping a small amount of starter and feeding it up to a larger target weight, everything above the amount you kept back is effectively what gets removed as discard before the next feeding, and higher ratios like 1:5:5 mean less of that gets wasted relative to how much active starter you end up with.

In a pinch, active starter can usually stand in for discard in a discard recipe, since it's the same culture just at a different stage — the batter may ferment a bit more and taste slightly milder, but the result is generally fine. The substitution doesn't work as cleanly in reverse: a recipe that names "active starter" as its leavening agent is depending on real rising power discard has already lost, so swapping in discard there risks a dense, flat loaf rather than a minor flavor difference.