How Much Levain Do I Need? Build Enough for Your Recipe and Next Feed
Work backward from 150 g levain plus a 20 g reserve. See the seed, flour and water amounts, including how different starter hydrations change the feed.
Separate the recipe amount from the reserve
If the dough needs 150 g levain and you want 20 g left for a future feed, build 170 g. The reserve stays outside the dough formula. Putting all 170 g into a recipe written for 150 g changes both its flour and water totals.
The reserve field is an amount you choose, not a recommended minimum. You can set it to zero if you keep a separate mother starter. Allow for any expected jar or spoon losses by increasing your chosen reserve; the calculator does not add a hidden allowance.
Work backward from a 1:3:3 feed
Here the seed and finished levain both have 100% hydration, meaning equal flour and water by weight. A 1:3:3 feed has seven weight parts: one seed, three fresh flour and three fresh water. For 170 g, one part is 170 ÷ 7 = 24.2857 g.
Use 24.3 g seed starter, 72.9 g flour and 72.9 g water. Rounded weights sum to 170.1 g; unrounded values total exactly 170 g. At readiness, use 150 g in the recipe and keep the chosen 20 g reserve. The ratio is by weight, not volume.
| Ingredient | Total levain |
|---|---|
| Seed starter | 24.3 g |
| Fresh flour | 72.9 g |
| Fresh water | 72.9 g |
| Total levain | 170.0 g |
| Levain needed for the recipe | 150.0 g |
| Reserve for your next feed | 20.0 g |
Different seed hydration changes the water addition
The builder’s ratio field specifies fresh flour per gram of seed. It calculates fresh water to achieve the final hydration, counting water already in the seed. This makes the same field useful with a stiff or liquid starter.
For 170 g finished levain at 100% hydration, a 50% hydration seed and flour ratio of 3 need about 23.2 g seed, 69.5 g fresh flour and 77.3 g fresh water. That is approximately 1:3:3.33, not 1:3:3. If the target would require removing water already in the seed, the tool shows an error.
Carry only the recipe portion into the dough
Open the example, enter your recipe amount and reserve, and check the seed hydration. Copy or share the feed amounts. The recipe-converter link passes the needed portion and the finished hydration; it deliberately leaves the reserve out.
This tool calculates ingredient weights. It does not predict a peak time or decide whether a starter is ready. Feeding ratio, temperature, flour and culture condition affect the process. Use your established observations and recipe instructions for fermentation, and recheck the dough’s total flour and water when changing levain hydration.