Calculating your flour to add is straightforward once you know the Sourdough Starter Feeding formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Sourdough Starter Feeding Calculator.
What is Sourdough Starter Feeding?
The Sourdough Starter Feeding calculation tells you your flour to add from a few simple inputs. The figure you are solving for here is the flour to add.
The Sourdough Starter Feeding formula
The core formula is:
Flour to add = Starter weight × Flour ratioHere is what each input means:
- Starter weight — a value measured in g. Example: 50 g.
- Flour ratio — a number. Example: 1.
- Water ratio — a number. Example: 1.
How to calculate it step by step
- Write down the starter weight (for example, 50 g).
- Write down the flour ratio (for example, 1).
- Write down the water ratio (for example, 1).
- Apply the formula above to get your flour to add.
- Double-check the result with the Sourdough Starter Feeding Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Starter weight | 50 g |
| Flour ratio | 1 |
| Water ratio | 1 |
| Flour to add | 50 |
| Water to add | 50 |
| Total after feeding | 150 |
With starter weight of 50 g, flour ratio of 1 and water ratio of 1, the flour to add works out to 50.
Example 2
With starter weight of 100 g, flour ratio of 1 and water ratio of 1, the flour to add works out to 100.
| Result | Value |
|---|---|
| Flour to add | 100 |
| Water to add | 100 |
| Total after feeding | 300 |
Example 3
With starter weight of 25 g, flour ratio of 1 and water ratio of 1, the flour to add works out to 25.
| Result | Value |
|---|---|
| Flour to add | 25 |
| Water to add | 25 |
| Total after feeding | 75 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Sourdough Starter Feeding Calculator does it instantly, for free, with the formula and a worked example built in.
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