Sourdough levain build calculator

Enter the ratio in seed, flour, and water order, such as 1:2:2, and the calculator scales every part from the seed you have available. It also gives the final levain weight, making it easier to prepare the amount a recipe needs without mental arithmetic, accidental ratio reversals, or inconsistent builds from one bake to the next.

Read the levain ratio in the correct order

A levain build ratio describes three weights in a fixed order: ripe starter seed, fresh flour, and fresh water. A 1:2:2 build therefore means one part seed, two parts flour, and two parts water. If you begin with 20 grams of seed, one part is 20 grams, so the build needs 40 grams of flour and 40 grams of water. The completed levain weighs 100 grams. The calculator uses exactly this scaling rule and does not treat the ratio as baker's percentage or as the hydration of the seed. Keeping those ideas separate matters because the flour and water already inside the seed are not being measured by this input. If your process records ratios with a seed term other than one, enter that term as well. For example, a 2:3:3 ratio with 20 grams of seed has a ten-gram ratio unit, producing 30 grams each of flour and water. Always confirm that your source writes the ratio in seed-flour-water order before relying on the result.

Choose a build that matches your schedule

The arithmetic tells you how much to feed, while fermentation time still depends on starter activity, flour choice, water temperature, room temperature, and the chosen inoculation. A build with more fresh flour and water relative to its seed generally has more food available and may take longer to mature than a build with a larger seed share under otherwise similar conditions. That relationship is useful when planning, but it is not a timer: observe the levain's rise, aroma, texture, and the maturity cues appropriate to your recipe. Use the calculator to remove measurement uncertainty, then apply your normal fermentation judgment. Weigh the seed first, add the displayed flour and water, and mix until no dry flour remains. The total shown is the combined weight immediately after mixing. Small differences caused by flour left on a spoon or water retained in a container can matter in tiny builds, so a scale with suitable resolution is helpful. The result is deterministic, so saving the same inputs provides a repeatable build record.

Scale for the levain amount your dough requires

You can work backward from a recipe by testing a seed weight that produces a total close to the levain quantity required. For a 1:2:2 build, the total contains five ratio parts, so a recipe needing 150 grams of levain can be built from 30 grams of seed, 60 grams of flour, and 60 grams of water. Consider making a modest practical allowance if your container and mixing tool retain some levain, but keep that allowance in your chosen seed weight rather than silently changing the ratio. The calculator reports grams and accepts decimal weights, which supports both small test builds and larger production batches. It rejects zero, negative, missing, nonnumeric, infinite, and excessively large values instead of guessing what was intended. This makes it suitable for recipe sheets and automated bakery calculations as well as manual use. The API price is $0.002 per request. Because the calculation uses no network, random value, clock, or fermentation prediction, identical valid inputs always return identical flour, water, total, and ratio values.