The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Calculate flour amount in starter

  • Pin It
BrianOD's picture

Calculate flour amount in starter

I'm trying to calculate the amount of flour (and water) in a certain number of grams of starter. The hydration is at 60%. I know that in 160 grams of starter, there are 100 g of flour and 60 of water, but what if I have a smaller or larger amount of starter in my recipe?

Here's the calculation
F= amount of flour
T = Total weight of starter
H=Hydration percentage
(F*H)=amount of water


T is known
H is known
I'm trying to solve for F and thereby find W (Water amount)

I just want to say that this website has been tremendously helpful, both in information and moral support. I'm baking loaves these days that I'm very pleased with and am now trying to "tweak" my formulas on a spreadsheet for timing and adjusting overall hydration.





Janetcook's picture

The way I figure out how much water and flour to use in a formula is by first finding out how much flour I want pre fermented and then the rest is simple.

I generally use 15% of the total flour in most of my breads in my starter.

If I am using 500g of flour I first multiply 500 by 15% to get the amount of flour to use in my starter:

500x15% =75g

I now know I need 75g of flour so the next step is to figure out the HL I am seeking.  I will use 60% since that is what you specified above.  I merely multiply again:


Now I know I need 45g of water.

When I add the flour and water I then know the total amount of starter I will end up with:

75+45=120g that has a hydration level of 60%

I know there are other ways to come up with the figures I have given you and maybe someone else will chime in with their method that may be more of what you are seeking.

If you can get your hands on a copy of 'Bread' by Jeffrey Hamelman there is much written about baker's math and it is written in a very easy to understand format.

Good Luck,



BrianOD's picture

Thanks Janet, but what I was trying to do was get the numbers for flour and water for a specific amount of starter at a specific hydration. That way I have those numbers to calculate the hydration of the final dough.

I figured out that

(starterhydrationaspercentage*100)/(100+starterhydrationaspercentage*100)*total grams of starter

will calculate the water in the starter, then its just subtracting that amount from the "total grams of starter " amount

I've got Jeff's book, which is terrific. This is where I read that a lower hydration starter will promote a more heterofermentative process and hence more of a "sour" bite to my bread. In keeping with his penchant for experimentation I'm playing with changing the starter hydration while maintaining the overall hydration in a recipe to see how it affects the final outcome. My spreadsheet will now calculate the overall percentage taking into account the amount of flour and water in the specific hydration of the starter.

I know this isn't the only factor (time & temp come into play), but I figured if I isolate one variable at a time, I'd be able to more effectively tweak my recipe.

thanks again for your help, this website is wonderful!


dmsnyder's picture

Hi BrianOD.

Here's the general method ... I should say, one general method of solving your problem:

1. Using baker's math, your 60% hydration starter has 160 parts, since flour is always 100% and the water is 60% of the flour. 

2. Divide T (total weight of your starter) by 160. This gives you the weight of each part. Let's call this number C (for conversion factor).

3. Multiply each ingredient's baker's percentage by C. This gives you the weight of each ingredient in your starter.

So, let's take a simple example. You have 100g of a 60% hydration starter. All the starter is AP flour. So, your formula in baker's percentages is:

Flour = 100% 

Water = 60%

Total % = 160.

So ....

100g of starter ÷ 160 = 0.625

Flour wt. = 100 x 0.625 = 62.5g

Water wt. = 60 x 0.625 = 37.5g

There you have it!

Note that this works just as well for mixed flour starters. For example, I often use a starter that is 70% AP + 20% WW + 10% Rye flour. To find the weight of each in 100g of 60% hydration starter, I would just multiply the percentage of each flour times 0.625. It works just as well for differing weights of starter and differing hydrations. You just need to know the baker's formula and the total amount of starter you end up with.

Easy peasy, eh?

Happy baking!


DavidEF's picture

Brian, I just wanted to second what David said above. The conversion factor "C" is really the trick, and once you know how to use it, you can use it for lots of other things besides finding the amount of flour in your starter. I'd just like to add one little thought about what that number actually represents. David said it is "the weight of each part" and I wanted to emphasize that it is a single unit of measure, in this case, of your starter. I've used this math to find how small a unit I could get down to with my starter, for less waste, while still being easy enough to weigh out and mix the flour and water.

But, the same trick can be used with bread dough too. Once you know "C" you can very easily scale your recipes, change hydration percents, mix in any amount of different flours (as David noted) and experiment to your heart's content, with one corner grounded to your original formula. The variable "C" is your basic building block for bakers' math and formulas. Use it well!

BrianOD's picture

Thanks guys, your math is much simpler than mine. I'll use it in the cell. I can see knowing the "C" coming in handy further down the road also!

dabrownman's picture

similar way to David's that i use all the time is" 172% (100% flour and 72% water) is alsoexpressed as 1.72.  Dividing the total weight... say 134 g by 1.72 gives you the weight of flour or 78 g  and 134 -78 = 56 g of water.  To check 78 + 56 = 134 g.