The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Wet Starter v. Firm Starter and Hydration Percentages

hydestone's picture

Wet Starter v. Firm Starter and Hydration Percentages

For the past month I've been working on a new sourdough starter and it is doing well.  I used the rye flour and pineapple juice method described in the handbook.  I've been mixing 1/4 cup starter, 1/4 cut of flour and 2 T of water each day for the past week or so.  I am going to make the San Francisco stlye sourdough in the lessons section.  It requires 300 g of starter and I don;t have that much.

I read in the starter maintenance section of the handbook to use 1/4 c starter, 1/2 c flour and 4 T water.  I wanted to make sure I had some left over to keep growing so today I mixed 1/2 c starter (everything I had) 1 c flour and 8 T of water.

I changed the ratio from 1/4 c starter:1/4 flour:2 T which I used to grow the starter.  Now I have 1/2c starter:1 c flour: 8 T water.

I am trying to figure out:

What ratios do I use when I want to produce larger quantities of starter to bake with?

How does % hydration work?  I thought 100 g flour with 50 g water = 50% hydration.  I am not sure how it works with a starter.

How can I take a wet starter and make a starter with 66% hydration?

I am going back to using a scale to bake and getting away from cups and T for a bit more accuracy.



dmsnyder's picture

Hi John.

First, do weigh ingredients, even when feeding your starter.

Second, you are correct regarding how hydration is calculated. In fact, the baker's percentage of any ingredient is represented by the formula:

(Ingredient weight/Total flour weight) x 100 = Baker's % of Ingredient

So, if Ingredient = water, then Hydration = (Water wt./Total flour wt.) x 100.

When changing the hydration of a starter for a particular recipe, usually the amount of your seed starter is small enough that the seed starter hydration need not be accounted for. (If you are computing everything to 3 decimal places, please don't let me stop you from factoring in the actual amount of water and flour in your seed starter.)

So, take the final starter feeding specified in the recipe you are using and ignore your seed starter hydration.

How can I take a wet starter and make a starter with 66% hydration?


10 g Active Starter (of any hydration between 50 and 125%)

30 g Flour

20 g Water

This will yield 60 g of 66% hydration starter.  Note that the difference in the water content between 10 g of a 50% hydration starter (very firm) and 10 g of a 125% hydration starter (very liquid) is approximately 1 g. (1 g/60 g) x 100 = 1.67% difference in your starter. Not enough to lose sleep over.

Hope this helps.


scamp's picture


Note that the difference in the water content between 10 g of a 50% hydration starter (very firm) and 10 g of a 125% hydration starter (very liquid) is approximately 1 g.


10g of 50% starter is 3.33g water and 6.66g flour. 

10g of 125% starter is  5.56g water and 4.44g flour.

That's more than a gram of water, and additionally, when you talk about a constant mass of dough, taking away a portion of water means adding that much flour, so the effect compounds.

That's a different of 2.2g each of flour and water.  In the wet starter case, you'll end up with a hydration of (25.56/34.44) = 74.2% and with the stiff starter you'd have a hydration of (23.33/36.66) = 63.6%.  That's a nontrivial difference.

That said, I agree with you that weighing, and getting something that's consistent is more important than worrying about exact hydration figures.  The recipe can always be adjusted over time.


dmsnyder's picture

I apologize for my sloppy math, and now feel obligated to make amends by providing a more accurate answer to John's original question.

To make a 66% hydration starter from a 125% seed starter:

Assume your seed starter will provide 25% of the total flour in the final starter.

Assume you want to make 100 g of final starter.

The total content of the final starter should be 40.33 g of water and 60.67 g flour.

Then the amount of flour in the seed starter should be 60.67 x 0.25 = 15.17 g. 

If the seed starter is 125% hydration, the water content would be 15.17 x 1.25 = 18.96 g.So, the total seed starter weight would be 18.96 + 15.17 = 34.13 g.

Subtracting the water in the seed starter from the total water in the final starter (40.33 - 18.96), you would need to mix the 34.13 g of seed starter with 21.37 g of additional water.

The amount of flour to add to this would be the total flour minus the flour in the seed starter, or 60.67 - 15.17 = 45.5 g.

Thus, the formula to make 100 g of 66% hydration starter, starting with a 125% hydration seed starter, would be:


Seed starter 34.13 g

Water 21.37 g

Flour 45.5 g

Total 101 g (due to rounding to 2 decimal places)


Of course, if the total amount of starter you want to make or the amount of pre-fermented flour you want in your starter changes, the numbers change. But the way to do the calculations is the same.

Please accept my apology for my previous, misleading advice.


GSnyde's picture

How would I convert that to cubic yards?



dmsnyder's picture

Hi, Glenn. 

I need to remind you: It is better to measure ingredients by weight rather than volume. But since you are such a jewel, I've converted the formula to carets for you:

Seed starter 170.65 ct

Water 106.85 ct

Flour 227.5 ct

Total 505 ct


sphealey's picture

Old Will Knot carries at least one scale that measures in each of these units:

Grams (g)
Kilograms (kg)
Milligrams (mg)
Ounces (oz)
Pounds (lb)
Troy Ounces (ozt)
Pennyweight (dwt)
Carats (ct)
Taels (Singapore)
Taels (China)
Stone (UK)

and at one point while researching scales I found one jewelry scale that would measure around 30 different jewelry-related units - most of which I had to look up on Wikipedia.  SI, ANSI, and Imperial are _not_ the only measuring systems out there still in use!


Candango's picture

David,  Yours was a great calculation, direct and easy to follow, (even in cubic inches).



hydestone's picture

Ok, let's take a specific example with no assumptions.


My seed starter is of an unknow hydration percentage.  Most recent feeding was 100g s + 100g f + 100g w.  Would this be roughly a 100% hydration seed starter?

So, assuming it is 100% hydration seed starter, 100g of seed starter contains 50g flour and 50g water.

I need 500g of 66% hydration seed starter for a recipe.

How do I figure out how much of the seed starter to use?  Once I determine this, I can calculate the rest...I am missing a step.

How did you come up seed starter accounting for 25% of total flour?

If I was using 80g of seed starter then I would have 40g flour and 40g water.  At 66% hydration does that ean I would use the following:

80g starter (40g flour and 40g water)

252g flour

168g water

500g total weight

scamp's picture

100g unknown + 100g water + 100g flour is roughly 100% starter, yes.  If you started with a very firm, 50% hydration starter you could have as little as 133g water and as much as 166g flour, which is about 80% hydration.  Or on the other extreme, a very liquid 125% starter would give you 155g water and 145g flour, which is 107%.  So if you have a reasonably liquid starter, and you triple it, and then use a small portion of it in a recipe, the error will get progressively smaller, and you should be just fine.

How much seed starter to use depends on the recipe and what you're trying to achieve.  In general, using less starter will increase favorable conditions for lactobacilli growth (which prefer the higher pH of more dilution) and will require longer rises.  The well-known 1:2:3 recipe is, obviously, 1/6th seed starter.

Your math is close.  66% hydration dough is 3 parts flour to 2 parts water (since 100/66 = 3/2).  500g of dough @ 66% hydration is 300g flour and 200g water.  Subtract the flour and water in your starter (40g each, which is one of the reasons 100% starter is easy to work with) and you get 260g flour and 160g water as the rest of your ingredients. 

Don't forget to add salt! The standard 2% salt measure is also a baker's percentage, so for your 300g of flour you'd add 6g salt to hit 2%. 




dmsnyder's picture


How did you come up seed starter accounting for 25% of total flour?

You will find specification of the percent pre-fermented flour a conventional way of deciding the amount of pre-ferment (of any kind) to use in a formula. 25% is a common amount. That's all.

In scaling recipes made with pre-ferments, you need to think in terms of the total dough to calculate total ingredients. However, the ingredients you actually weigh are for the levain and for the "final dough," which is made from the levain  and the remaining ingredients.


For your specific example:

You want to make 500 g of dough at 66% hydration with 25% of the flour pre-fermented. Your seed starter is 100% hydration. Let's also assume 2% salt.

So, your formula in baker's percentage is:


Baker's %










One way of computing ingredient amounts is to calculate the "conversion factor." This is the total dough weight divided by the total baker's %.  So, 500/168 = 2.98 is the conversion factor for this formula.

To calculate the weight of each ingredient, you multiply the baker's percentage of each ingredient by the conversion factor. For your formula, the ingredient weights for the total dough would be:

Flour 100 x 2.98 = 298 g

Water 66 x 2.98 = 196.68 g

Salt 2 x 2.98 = 5.96 g

With rounding to 2 places, this adds up to 500.64 g.

Now, the final dough consists of the levain + the additional ingredients. The levain contains 0.25 x 298 = 74.5 g of flour and an equal weight of water for a total weight of 149 g. So, to mix the final dough, you need to subtract the water and flour in the levain from the amounts of flour and water in the total dough. Thus, to mix your final dough, you would use:

Flour 298 - 74.5 = 223 g

Water 196.68 - 74.5 = 122.18 g

Salt 5.96 g

Levain 149 g

With rounding, this adds up to 500.14 g of total dough.

This may seem unduly complicated, but it becomes pretty easy to work with, once you understand the underlying concepts and have run through the calculations a few times.



hydestone's picture

Thanks for the thorough explanations guys, I've got it.

What is the typical range for fermented flour?  15% to 35%?  I am sure there are many variables.


Are there any rules of thumb?