# What goes in my sourdough?

Works out a sourdough recipe from baker’s percentages: the flour, water, starter and salt to mix for a hydration you choose, counting the flour and water already in the starter.

- Page: https://www.acalculator.org/food/sourdough-calculator
- JSON spec: https://www.acalculator.org/food/sourdough-calculator.json
- Version: c8ca9fdcdb53

## Default answer

Example with the default inputs (Start from Total flour, Total flour 500 g, Hydration 70%, Starter 20%, Salt 2%, Starter hydration 100%): Mix 450 g flour, 300 g water, 100 g starter and 10 g salt.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | Start from | The total flour you want to use, or the dough weight you want to end with. |
| f | Total flour | All the flour in the dough, including the flour in the starter. |
| d | Dough weight | The weight of dough you want, for example for one loaf. |
| h | Hydration | Total water as a percent of total flour, counting the starter. |
| s | Starter | Starter (levain) weight as a percent of total flour. |
| salt | Salt | Salt as a percent of total flour. |
| sh | Starter hydration | Water in the starter as a percent of the flour in it; 100% is equal weights. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| addFlour | Flour to add | Total flour minus the flour in the starter. |
| addWater | Water to add | Total water minus the water in the starter. |
| starterWeight | Starter | Starter % × total flour. |
| saltWeight | Salt | Salt % × total flour. |
| totalFlour | Total flour | All the flour, including the starter’s. |
| totalWater | Total water | Hydration × total flour, including the starter’s water. |
| doughWeight | Dough weight | Total flour + total water + salt. |

## Method

Total water = hydration × total flour; starter = starter % × total flour; salt = salt % × total flour. The starter holds starter ÷ (1 + starter hydration) of flour and the rest water, so flour to add = total flour − starter flour and water to add = total water − starter water. From a dough weight D, total flour = D ÷ (1 + hydration + salt).

## Assumptions

- Every percent is of the total flour, including the flour in the starter (baker’s percentages).
- The starter is only flour and water, at the starter hydration you give (100% means equal weights).
- Weights are as mixed; water lost in baking is not modelled.

## Worked examples

1. from = flour, f = 0.5, h = 70%, s = 20%, salt = 2%, sh = 100% gives addFlour = 0.45, addWater = 0.3, starterWeight = 0.1, saltWeight = 0.01, doughWeight = 0.86. Source: Wikipedia, Baker percentage (each ingredient as a percent of the flour weight; the water percent is the hydration; flour weight = dough weight ÷ the sum of the percentages), https://en.wikipedia.org/wiki/Baker_percentage (retrieved 2026-10-02).
2. from = dough, d = 0.9, h = 75%, s = 20%, salt = 2%, sh = 100% gives totalFlour = 0.508475, addWater = 0.330508, doughWeight = 0.9. Source: Wikipedia, Baker percentage (each ingredient as a percent of the flour weight; the water percent is the hydration; flour weight = dough weight ÷ the sum of the percentages), https://en.wikipedia.org/wiki/Baker_percentage (retrieved 2026-10-02).
3. from = flour, f = 1, h = 65%, s = 30%, salt = 2.2%, sh = 50% gives addFlour = 0.8, addWater = 0.55, starterWeight = 0.3, saltWeight = 0.022. Source: Wikipedia, Baker percentage (each ingredient as a percent of the flour weight; the water percent is the hydration; flour weight = dough weight ÷ the sum of the percentages), https://en.wikipedia.org/wiki/Baker_percentage (retrieved 2026-10-02).

## FAQ

### What is hydration in sourdough?

The weight of all the water divided by the weight of all the flour, as a percent. 350 g of water to 500 g of flour is 70% hydration. Higher hydration gives a wetter, more open dough.

### Does the starter count toward hydration?

Yes, on this page. A starter is flour and water, so its flour is part of the total flour and its water part of the total water. 100 g of starter at 100% hydration adds 50 g of each, so a 500 g flour, 70% dough needs only 450 g more flour and 300 g more water.

### What are baker's percentages?

Each ingredient as a percent of the total flour, which is always 100%. A 500 g flour dough at 70% water, 20% starter and 2% salt has 350 g water, 100 g starter and 10 g salt.

### How much starter should I use?

Recipes often use 10% to 30% of the flour weight. More starter rises faster; less gives more time to ferment. The page takes any value from 0% to 100%.

### How do I get a dough of a set weight?

Choose dough weight. The total flour is the dough weight divided by 1 + hydration + salt: 900 g at 75% hydration and 2% salt needs 900 ÷ 1.77 = 508 g of total flour.

### What if my starter is stiff?

Open More options and set the starter hydration. A 50% starter has twice as much flour as water: 300 g of it holds 200 g of flour and 100 g of water.

## Sources

- Wikipedia, Baker percentage (each ingredient as a percent of the total flour weight; the water percent is the hydration; flour weight = dough weight ÷ the formula percentage). https://en.wikipedia.org/wiki/Baker_percentage (retrieved 2026-10-02)