This article has 9 examples which will teach you how to:

- Calculate sourdough starter hydration
- Calculate sourdough starter hydration when you combine two sourdough starters
- Increase and decrease sourdough starter hydration
- Calculate sourdough bread hydration

## What is Baker’s Percentages?

**The quantity of ingredients in a sourdough bread recipe is expressed using baker’s percentages, which states the weight of every ingredient as a percentage of the total weight of flour called for in the sourdough bread formulation. **

**The total weight of flour always corresponds to 100%**, while the percentages of every other ingredients is in relation to it.

From examples 1 and 2 below you can see that no matter what the weight of the flour is, it always corresponds to 100% baker’s percentages. This is an **important rule to remember** that will help us in calculating our sourdough bread and sourdough starter hydration.

Example 1:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 1000g |

Water | 75% | 750g |

Salt | 2% | 20g |

Example 2:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 600g |

Water | 75% | 450g |

Salt | 2% | 12 |

## How to calculate sourdough starter hydration?

**Example 3: What is the sourdough starter’s hydration for a mixture of 70g of flour and 88g of water?**

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 70g |

Water | ? | 88g |

Baker’s Percentage Ratio as follows:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **water percentage variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Water Percentage (Hydration) = (Total Water Weight/Total Flour Weight) x Flour Percentage*

Now we can substitute all the known quantities from the table into the right side of the equation:

*Total Water Weight = 88g*

*Total Flour Weight = 70g*

*Flour Percentage = 100%*

*Water Percentage = (Total Water Weight/Total Flour Weight) x Flour Percentage*

*Water Percentage = (88g/70g) x 100%*

*Water Percentage = 126% *

*Sourdough starter hydration = Water Percentage*

*Sourdough starter hydration = 126%*

**Example 4: What is the amount of water required to achieve a 90% hydration starter with 50g of flour?**

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 50g |

Water | 90% | ? |

Baker’s Percentage Ratio as follows:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **total water weight variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

Now we can substitute all the known quantities from the table into the right side of the equation:

*Water Percentage = 90%*

*Flour Percentage = 100%*

*Total Flour Weight = 50g*

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

*Total Water Weight = (90%/100%) x 50g*

*Total Water Weight = 45g*

## How to calculate sourdough starter hydration when you combine two sourdough starters?

**Example 5: What is the new sourdough starter hydration, when you combine two sourdough starters of a known hydration level?**

Sourdough Starter 1:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 50g |

Water | 80% | 40g |

Sourdough Starter 2:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 50g |

Water | 100% | 50g |

First, we have to calculate the combined total flour weight, and combined water weight:

*Combined Total Flour Weight = Flour Weight of Starter 1 + Flour Weight of Starter 2*

*Combined Total Flour Weight = 50g + 50g*

*Combined Total Flour Weight = 100g*

*Combined Total Water Weight = Water Weight of Starter 1 + Water Weight of Starter 2*

*Combined Total Water Weight = 40g + 50g*

*Combined Total Water Weight = 90g*

We can draw up a new table for the **combined sourdough starter**:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 100g |

Water | ? | 90g |

Similar to example 3, we can **calculate the combined sourdough starter hydration** using the baker’s percentage ratio:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **water percentage variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Water Percentage (Hydration) = (Total Water Weight/Total Flour Weight) x Flour Percentage*

Now we can substitute all the known quantities from the **combined sourdough starter table** into the right side of the equation:

*Total Water Weight = 90g*

*Total Flour Weight = 100g*

*Flour Percentage = 100%*

*Water Percentage = (Total Water Weight/Total Flour Weight) x Flour Percentage*

*Water Percentage = (90g/100g) x 100%*

*Water Percentage = 90% *

*Combined sourdough starter hydration = Water Percentage*

*Combined sourdough starter hydration = 90%*

## How to increase and decrease sourdough starter hydration?

**Example 6: How much water should I add to my sourdough starter to increase its hydration level?**

**Let’s say we want to increase our old sourdough starter of 80% hydration to 110% hydration,** **we have to only add water.**

Old Sourdough Starter:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 100g |

Water | 80% | 80g |

New Sourdough Starter:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 100g |

Water | 110% | ? |

To calculate much water we need to add to our sourdough starter:

*Weight of water to be added = New sourdough starter water weight – Old sourdough starter water weight*

Since we already know the old sourdough starter water weight, which is 80g, we only have to **calculate the ****new sourdough starter water weight**.

Using the baker’s percentage ratio on our new sourdough starter:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **total water weight variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

Now we can substitute all the known quantities from the **new sourdough starter table** into the right side of the equation:

*Water Percentage = 110%*

*Flour Percentage = 100%*

*Total Flour Weight = 100g*

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

*Total Water Weight = (110%/100%) x 100g*

*New sourdough starter water weight = 110g*

Going back to the equation to calculate the weight of water to be added:

*New sourdough starter water weight = 110g*

*Old sourdough starter water weight = 80g*

*Weight of water to be added = New sourdough starter water weight – Old sourdough starter water weight*

*Weight of water to be added = 110g – 80g*

*Weight of water to be added = 30g*

**Example 7: How much flour should I add to my sourdough starter to decrease its hydration level?**

**Let’s say we want to decrease our old sourdough starter of 80% hydration to 70% hydration, we have to only add flour.**

Old Sourdough Starter:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | 100g |

Water | 80% | 80g |

New Sourdough Starter:

Ingredients | Baker’s Percentages | Total Weight |

Flour | 100% | ? |

Water | 70% | 80g |

To calculate much flour we need to add to our sourdough starter:

*Weight of flour to be added = New sourdough starter flour weight – Old sourdough starter flour weight*

Since we already know the old sourdough starter flour weight, which is 100g, we only have to **calculate the ****new sourdough starter flour weight**.

Using the baker’s percentage ratio on our new sourdough starter:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **total flour weight variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Total Flour Weight = (**Flour Percentage/Water Percentage) x Total Water Weight*

Now we can substitute all the known quantities from the **new sourdough starter table** into the right side of the equation:

*Flour Percentage = 100%*

*Water Percentage = 70%*

*Total Water Weight = 80g*

*Total Flour Weight = (**Flour Percentage/Water Percentage) x Total Water Weight*

*Total Flour Weight = (100%/70%) x 80g*

*New sourdough starter flour weight = 114g*

Going back to the equation to calculate the weight of flour to be added:

*New sourdough starter flour weight = 114g*

*Old sourdough starter flour weight = 100g*

*Weight of flour to be added = New sourdough starter flour weight – Old sourdough starter flour weight*

*Weight of flour to be added = 114g – 100g*

*Weight of flour to be added = 14g*

## Calculating Sourdough Bread Hydration

**Example 8: What is the sourdough bread’s hydration level, given a known weight of flour and water?**

We may come across a scenario where we found a sourdough recipe that only state the total weight of flour and water and we would like to calculate its hydration level.

Sourdough Bread Total Formula:

Ingredients | Baker’s Percentages | Total Weight |

New Flour | ? | 900g |

New Water | ? | 600g |

Oil | ? | 50g |

Salt | ? | 20g |

Starter’s Flour | ? | 100g |

Starter’s Water | ? | 100g |

**The new flour is the flour that we will add on top of the starter that we will be using, and the new water is water that we will also add on top of the starter to form our final dough.**

To calculate the hydration of our sourdough bread, we can use the baker’s percentage ratio:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **water percentage variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Water Percentage (Hydration) = (Total Water Weight/Total Flour Weight) x Flour Percentage*

**To get the total water weight of the dough, we have to sum up the new water’s weight, the starter’s water weight, and the weight of the oil. Oil and milk is a liquid at room temperature, hence it is included in the hydration calculation of our sourdough bread.**

*Total water weight in dough = New water weight + Starter’s water weight + Oil weight*

*Total water weight in dough = 600g + 100g + 50*

*Total water weight in dough = 750g*

**To get the total weight of flour in the dough, we need to sum up the new flour’s weight and the starter’s flour weight.**

*Total weight of flour in dough = New Flour weight + Starter’s Flour weight*

*Total weight of flour in dough = 900g + 100g*

*Total weight of flour in dough = 1000g*

**The total dough flour weight always corresponds to 100% baker’s percentage.**

Hence the new flour’s weight of 900g is **90% baker’s percentage**, and the starter’s flour weight of 100g has **10% baker’s percentage** (or 10% innoculation).

In this example the starter’s hydration is 100%, since the starter’s flour weight is the same as the starter’s water weight. Hence the** starter’s water baker’s percentage is also 10%** which is the same as the starter’s flour baker’s percentage.

Now we can substitute all the known quantities from our calculations above into the right side of the baker’s percentage ratio equation:

*Total Water Weight = 750g*

*Total Flour Weight = 1000g*

*Flour Percentage = 100%*

*Water Percentage = (Total Water Weight/Total Flour Weight) x Flour Percentage*

*Water Percentage = (750g/1000g) x 100%*

*Water Percentage = 75% *

*Sourdough bread hydration = Water Percentage*

*Sourdough bread hydration = 75%*

**Example 9: What is the amount of water required to achieve a 80% hydration level sourdough bread?**

Let’s say we have decided that we would like to bake an 80% hydration sourdough bread, with **total flour in the dough to be 500g, and a 10% sourdough starter innoculation of 100% hydration**. We would like to know how much water we should add to the dough to achieve the 75% hydration.

Sourdough Bread’s Total Formula:

Ingredients | Baker’s Percentages | Total Weight |

New Flour | 90% | 450g |

New Water | 65% | ? |

Oil | 5% | 25g |

Salt | 2% | 10g |

Starter’s Flour | 10% | 50g |

Starter’s Water | 10% | 50g |

**The new flour is the flour that we will add on top of the starter that we will be using, and the new water is water that we will also add on top of the starter to form our final dough.**

If we add the new water’s baker’s percentage (65% hydration), the starter’s water’s baker’s percentage (10% hydration), and the oil’s baker’s percentage (5% hydration), we will arrive at the 80% hydration of our sourdough bread.

To calculate the **new water weight**, we can use the baker’s percentage ratio:

*Water Percentage/Flour Percentage = Total Water Weight/Total Flour Weight*

By keeping only the **total water weight variable** on the left side of the equation, and moving every other variable on the right side, we get:

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

To get the total water weight of the dough, we have to sum up the new water’s weight, the starter’s water weight, and the weight of the oil. Oil and milk is a liquid at room temperature, hence it is included in the hydration calculation of our sourdough bread.

Total Water Weight = New Water Weight + Starter’s Water Weight + Oil Weight

We can plug this into our baker’s percentage ratio equation:

*Total Water Weight = (**Water Percentage/Flour Percentage) x Total Flour Weight*

*New Water Weight + Starter’s Water Weight + Oil Weight **= (**Water Percentage/Flour Percentage) x Total Flour Weight*

*New Water Weight = [**(**Water Percentage/Flour Percentage) x Total Flour Weight] – Starter’s Water Weight – Oil Weight*

Remember that the total dough flour weight always corresponds to 100% baker’s percentage.

Now we can substitute all the known quantities from the table above into the right side of the equation:

*Water Percentage = 80%*

*Flour Percentage = 100%*

*Total Flour Weight = 500g*

*Starter’s Water Weight = 50g*

*Oil Weight = 25g*

*New Water Weight = [**(**Water Percentage/Flour Percentage) x Total Flour Weight] – Starter’s Water Weight – Oil Weight*

*New Water Weight = [**(**80%/100%) x 500g] – 50g – 25g*

*New Water Weight = [400g] – 50g – 25g*

*New Water Weight = 325g*