What is 100% Hydration Sourdough Starter? (Full Guide)

Sharing a simple guide to understanding a 100% hydration sourdough starter along with a basic calculation for hydration in sourdough baking.

100% hydration sourdough starter

One of the most confusing parts of sourdough baking for me when I began was the whole topic of hydration and percentages within a sourdough recipe. Honestly, the moment I saw there was some math involved, I was reluctant to get in on the sourdough craze. I mean who wants to spend their time in the kitchen with a calculator? Certainly, not me.

It didn’t help things to realize there were different takes on sourdough and some very complicated articles on the topic, many of which contradict one another. Most using sourdough lingo I didn’t quite understand as a beginner. Leaving me often even more confused than when I began my search for the answer.

Eventually I found a basic calculation for factoring hydration levels but then shortly after I was met with more confusion. When a recipe called for a 100% hydration sourdough starter. I stood in my kitchen dumbfounded and frustrated. How was I supposed to know the hydration level in a starter I have had for years? Weren’t all starters the same?

When searching this, I didn’t find a simple answer. Just more uncertainty.

Today I would like to bridge this gap and give you a very straightforward explanation. Might I also add, that sourdough is an understanding more than anything else. Like most things, we can often over complicate the process. This is my effort to simplify sourdough and make it accessible to all the home bakers out there looking to bake the best bread of their lives.

What is Hydration?

The word itself might seem confusing. At least, I know it was for me. But to put it simply, hydration in sourdough refers to the amount of water versus flour in the dough or starter. One that is 100% hydration means that there are equal parts of flour and water within the recipe (or starter). That means that a 100% hydration sourdough starter would look something like 50g of water, and 50g of flour. This is a classic ratio for a standard sourdough starter.

Why is Understanding Hydration Useful?

It might seem too complicated or even unnecessary to factor in the concept of hydration. Trust me, I get it. However, hydration affects many things within sourdough baking and that is why it is such an important topic to cover. To keep it simple hydration will impact the crumb, the crust, the texture, and even the ability of ease to work with the dough itself.

Wetter dough that is higher in hydration will have a more open crumb and a thinner crust. What is more, these doughs are stickier and more complicated to work with. While lower hydration dough is easier to shape and much less sticky.

 For beginner bakers its best to stick to doughs with less water content (lower hydration), and then work your way up to a higher hydration level.

This will give you more success early on in your baking. Successfully baking a loaf of bread with your own sourdough starter can be a major milestone when learning and first starting out. You will feel more comfortable adjusting the hydration level of sourdough as your skills build.

Note: You can use a 100% hydration sourdough starter for both low-hydration and high-hydration recipes.

Basic Hydration Calculation

(Weight of Water divided by Weight of Flour) x 100

So for example, 300g of water divided by 400g of flour x 100= 75% hydration

A 100% hydrated sourdough starter would look something like this 50g water, divided by 50g flour x 100= 100%, pretty simple right?

As an Example:

Weight of Water

25g starter

300g water

Total: 325g

Weight of Flour

25g starter

400g flour

Total: 425g

Calculation: 325g water divided by 425g flour x 100= 76% hydration

Why is a 100% Hydration Sourdough Starter the Norm?

In the world of sourdough, the most common sourdough starter is that of a 100% hydration. This is when you feed the starter equal amounts of flour and water each time. Resulting in equal amounts of both flour and water within the starter. The wide use of these types of starters is all in its convenience.

When using a 100% hydration sourdough starter, it mixes into recipes easily, it is simple to maintain and is straightforward when first made. The best part is there is no need to worry about adjusting the hydration levels when mixing up a dough since the ratio for this starter is 1:1 you can skip accounting for it because it doesn’t change anything.

sourdough starter

Stiff Sourdough Starters

You may have heard the term stiff starter, or see bakers baking with what appears to be a stiffer starter. This is because as you grow more experienced with baking sourdough, you can play with the different hydration levels within the starter itself.

 A stiff starter has less water, which causes it to be as the name implies, a bit more stiff. Typically stiff starters have about 80% water in them. There really is only one key advantage to keeping a stiff starter over other starters and this is to reduce the need for frequent feedings.

When the starter is kept in a lower hydration level, it reduces the consumption of flour by wild yeast and bacteria. But before you go and decide a stiff starter is for you, there is a couple things to note.

First, a stiff starter is a little trickier to work with as it does not mix easily into the dough. Secondly, the flavor profile of a stiff starter tends to have a more pronounced sour taste. You may or not see this as a negative but it is worth noting. The pronounced sour taste is due to the slower fermentation process of a stiff starter.

The process of fermentation is longer as the bacteria and wild yeast move slower resulting in more acetic acid that intensifies the sour taste within the starter. The end result is a loaf or baked good with a more intense sourdough tang.

To create a stiff starter, you can divide a portion of your 100% hydration starter into another container, about one cup should do it. Feed the starter more flour than water using the basic hydration calculation above. For example, 80g of water and 100g of flour. This will be an 80% hydration ratio and will create a thicker starter. Allow it to ferment as normal. Check on it to ensure the bubbles are present and fermentation is taking place. Continue feeding it at a 80% hydration roughly.

What you are wanting is for the starter to have a thick consistency and ensure the bubbles are present. Once the starter is robust and active, you can use it just as you would the 100% hydration starter. The only thing that really changes is the flavor profile and the frequency of feedings will be less so. You will also need to factor in the starter in your hydration equation since it will no longer be a 100% hydration starter.

Liquid Sourdough Starters

On the other end are liquid starters. These as you might have already guessed, have more liquid than the above starters. Liquid starters typically have about 120% hydration in total and their consistency is very similar to a thin pancake batter. For this, the starter is very easy to mix into recipes and tends to have a quicker rise time. Which for many can be very beneficial. So if using one, it is good to keep a close eye on the recipe.

The downside is that these starters need to be fed much more frequently. This is because the microorganisms in this starter work much quicker at eating the flour within the starter and do so at a rapid rate. The flour will need to be replenished often. This is where a lot of people find liquid starters to be a little on the high maintenance side.

Now let’s discuss flavor for a moment. With a stiff starter, you will have a more intense flavor profile and distinct sourdough taste. On the contrary, with a liquid starter, the flavor profile will be less intense due to the frequent feedings and shorter fermentation times. If you do not like the sour taste in sourdough, this starter might be worth exploring.

To create a liquid starter, divide your 100% hydration sourdough starter into another container. About 1 cup should do it. To make a liquid starter, you will do the opposite of the stiff starter by adding more water than flour. The total water needed will vary with the total amount of flour used. As an example: 120g for water and 100g of flour is 120% hydration.

Note: Use the basic hydration calculation and weigh your ingredients to get the most accurate results.

Remember you will need to do frequent feeding for this starter since the bacteria and yeast will be eating up the lesser amount of flour quicker.

The starter should have a thin pancake like consistency. You will want to ensure the bubbles are present in this starter to ensure that fermentation is taking place. After active, you can use the liquid starter as you would your other starter.

Benefits of a 100% Hydration Starter

There is good reason that 100% starters are so common and honestly one that most stick to most often. This starter is easy to make right at home with just water and flour, oh and a little patience. Once created the possibilities are endless. This starter can be mixed up and added to doughs with ease.

It is easy to maintain and has a medium flavor profile so it great for sweet recipes as well as savory baked breads. It also makes delicious sourdough pancakes as the consistency of this starter is perfect for creating the batter.

Want To Make a 100% Hydration Sourdough Starter?

A sourdough starter consists of just a few things. Flour, water, and wild yeasts. Wild yeast is captured through a process of fermentation wherein the wild yeast within the environment of the starter is captured and used to help leaven bread, naturally. The distinct visual evidence of this is the bubbles that form within the starter. When a starter has a 100% hydration ratio, these bubbles are pretty easy to spot.

If you are in the beginning stages of sourdough, you might not quite have a starter to work with or perhaps you are looking to make a 100% hydration sourdough starter. To make a new sourdough starter, I have written a simple guide that explains in full detail exactly how to make one right at home with just flour and water. This simple guide is how I made my own starter and how I continue to make starters for other people. I must say, they make a very nice homemade gift.

sourdough starter in a jar

Best Containers For a 100% Hydration Starter

There are many containers that work great for storing a sourdough starter. I like to use a standard 32 oz wide-mouth mason jar for mine. Not only is the container glass, which ensures there is nothing interfering with the wild yeast. It is also clear so I can see the condition of the starter easily and whether it is running low or not.

But it’s also super convenient as it fits perfectly in the fridge door for storage. While not taking up too much counter space when out. I have used my Pyrex dish to store my sourdough starter as well. This is useful as again, it is glass but also because you can make a larger amount this way if desired.

How Often Do I Feed a 100% Hydration Starter?

Feeding your starter will vary with use. If you leave your starter out on the counter and bake with it daily, you will need to feed it daily. However, if you house your starter in the fridge between uses, a general rule is to feed a starter about once a week.

Although I have waited longer and my starter was fine unfed at 2 weeks. Keep in mind starters are violate, and alive so even if you have a 100% hydration starter, it might not be as robust as mine and vice versa. So if you keep with the general rule of feeding once per week (if left in the fridge), your starter should maintain its healthy activity.

Float Test

If you are unsure whether your starter is active enough, a float test might be in order. This is a simple way to test your starter’s activity. Grab a glass of water and place a teaspoon of starter on top. If the starter floats, it contains enough gas to float on water and is ready to use for baking.

One thing to note is for liquid starters, if you decide to keep a liquid sourdough starter over a 100% hydration one, your starter might not float as easily. However, it might be ready to use. The thin consistency might make the starter smear into the water instead of sitting at the top. If you are sure your liquid starter has been fed properly and you are seeing plenty of bubbles. Don’t let the float test divert you from baking with it.


Do I have to use grams or can I measure in cups instead?

It is highly recommended to use grams (weight) over cups (volume). People tend to measure with cups incorrectly and in sourdough baking, this can make all the difference. The best way to to measure your ingredients accurately is to use a kitchen scale that way you can accurately measure the correct flour amount and water amount every time.  It might seem to be a little bit extra work, but once you adapt to using a kitchen scale it quickly becomes the easiest way to measure.

​Do I need to use filtered water?

A common misconception is that you need to use filtered water for your starter or to mix up doughs. It is perfectly fine to use tap water if it is clean enough to be drinking water. That is the standard, to use drinking water.

Does the type of flour matter for my starter?

You can use different flours for starters. I like to use an organic unbleached all purpose flour for my starter. However, any white flour will work. A couple things to note, in the past when using a bleached flour, the starter took on a more strong chemical smell almost like nail polish remover. Whereas when I use organic unbleached all purpose, the smell is sweet and almost yeast like. Both will work to rise bread but the smell is much more pleasant with the organic flour.

Sourdough Recipes You To Try

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