Help in working out starter hydration




I have been browsing this amazing sites for a couple of months now.. thanks to the useful advice I find on this sites I have some success in my sourdough journey.

I have been baking at least 2 loaf on every weekend for the last couple of months. I think I am ready to venture further. 

There are recipe on this sites I like to try.. the ingredient ask for 75% hydration starter, so far I have only use 100% hydration starter (equal weight of water and flour). Can I assume that 75% means 75% of water to 100% of flour. 

If the recipe ask for 185g of starter 75% hydration, would it be right to say I can achieve 75% with 80g water to 105g flour (76.1%), also would close enough be good enough or do should i really try to achieve 75% exactly.

Thank in advance,

JJ :)

262 users have voted.


farinam's picture
farinam 2011 September 9

Hello JJ,

Hydration is just the amount of water in the mix expressed as a percentage of the flour in the mixture so your assumption is correct.

When you are doing the calculations you also have to take into account the culture that you use to inoculate your starter/levain.

As an example, if you start with 90g of 100% culture, to make 185g of 75% levain you would need to add 61g of flour and 34g of water.

If you have any skill with spreadsheets such as Excel, the calculations are quite easy to do yourself.  Otherwise there are a number of hydration calculators available on the interweb either on-line or down-loadable.

Hope this helps.


Franz 2011 September 13

Hello jojo.

I fully agree with Farinam. Here is how I go about it (the hard way) when I have to do a conversion. The initial 90g is 45g water and 45g flour. I want to add another 95 g with a hydration that ends up with an overall 75% hydration. To end up with an overall hydration of 75%, I divide 1 85g by 1.75 (wich is 1 part flour and 0.75 part water) = 105.71g flour and 79.28g water. I subtract from the 79.28g the 45g water from the initial 90g @ 100% = 34.28g. I subtract from the105.71g the initial 45g flour from the 90g @ 100%= 60.71g. After you added 60.71g flour and 34.28g water to the original 90g @ 100%, you end up with 185g @ 75%.

It sounds a bit complicated as I explain it in detail, but it's not so bad after you get the hang of it. Good luck,


PetraR 2013 September 4

My starter will be 4 Month old soon, is doing great and bakes fantastic bread.

I take half out before each feed but do not weigh what is left in the container, just add 75 g of Water and 100 g of Flour.

I bake a loaf of Sourdough every 3 days  and often even 2 to give to friends.


farinam's picture
farinam 2011 September 26

Hello Lynn,

I have posted links to a couple of spreadsheets that you can download.

Hope this helps.  Let me know if you need more detail.


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