The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

Baker's Percentage of Sourdough Starter's picture

Baker's Percentage of Sourdough Starter

Hello everyone,

I'm having a hard time finding a definitive answer on this question.  Can anyone provide clarity?

Say you have a recipe that calls for:

- 800 g of Bread Flour

- 400 g of 100% hydration Sourdough Starter

- 420 g water

- 13 g salt


There are 4 different ways I can calculate the starter percentage in this recipe.  Please vote on which one you use or believe is correct:

1) Fermented Flour to Total Flour: = (400/2)/(800+200) = 200 / 1,000 = 20%

2) Fermented Flour to Non-Fermented Flour = (400/2)/800 = 200 / 800 = 25%

3) Total Starter to Total Flour = 400 / (800+200) = 400 / 1,000 = 40%

4) Total Starter to Non-fermented Flour = 400 / 800 = 50%


So what would you say?  Is the starter percentage in this recipe 20%, 25%, 40%, or 50%?


Thanks for your feedback, really interested to know the true way to do this!

Peace and blessings,




Yippee's picture



GaryBishop's picture

The first rule is "there are no rules!". The second rule is fermented flour / total flour = 20%.

Some recipes leave it out all together. Never made sense to me. The best recipes give you both the percentages and grams so you can work it out for yourself. 

UVCat's picture

i have seen #1 called the percent pre-fermented flour, which, as a bonus, is unambiguous. i have seen recipes specify this quantity as well as specifying the baker’s percent for the levain, so i think they are different things and probably should have different names. but, i’m no expert. :)

i find the percent pff more useful for understanding how the recipe works, but the baker’s percent of levain, which i would calculate as you do in #4, is most helpful to me in scaling a recipe up or down.

just my $0.02,


Rafe's picture

1. If you are using as two separate ingredients 200+200 to create the starter

4. If you are using premixed 400g as a single ingredient from a larger batch of starter.

JJ1&4's picture

I like your spreadsheet, thanks for providing!  The left side shows both the 20% of pre-fermented flour to total flour ratio, as well as the 24.49% of starter as a percentage of overall dough weight, and the right side shows that the starter (or preferment) has a 50% baker's percentage relative to the non-fermented flour.  It's interesting how the same concept can be expressed in many ways, and for novice or beginning bakers it's helpful to see this in order to aid in recipe interpretation.  I almost always find yeast-based recipes and convert to sourdough, and knowing how all of the math works is critical.

Every Highschool should have a baker's math class!

Rafe's picture

Hi Jake – You’re welcome

The left and right are two recipe cards created from a single master spreadsheet.

The master has the recipes on individual rows, giving the ability to add new, update old & compare numerous simultaneously. That and I can view both an original & revised weight side-by-side on the same recipe card. So, it was easy enough to put your two versions together.

As the sheet works out all the percentages (Non/Preferments & Hydrations), I only have to enter the ingredient weights. In the case of the 50% preferment, I just copied the sourdough section total and added the number to a new row along with the remaining ingredients, the sheet did the rest.

I agree that the concept can be expressed in many ways, so I tend to check several recipes at once, smoothing out flaws or just comparing quantities of ingredients, hence the multi-row sheet

But to save me going through the whole thing there is more information and a couple of full recipes here.

As for High school Baker’s math. No need I have a spreadsheet! 😉


GlennM's picture

You could make a case that you have 800+400+420 = 1620. That would be 24.69% of the total flour and water is preferment 😳

Rafe's picture

that 24.49% of the tdw is preferment's picture

I hadn't thought of it like that.  Using that idea, you could also say you have 12.35% as pre-fermented flour to total dough weight.

There are truly a lot of different ways to express the same thing, and the thing I'm learning from you all is that when someone provides a recipe but does not specify their method of calculation, you could end up with a vastly different amount of starter used; this could certainly contribute to an unexpected result!

Personally I like the idea of using pre-fermented flour to total flour as this disregards the starter's hydration percentage entirely.  Therefore, if you have two people who are using different hydration starters, they could still end up with the same amount of pre-fermented flour in their final recipes.

Thank you all for your interest, knowledge, and feedback!


Abe's picture

It'll still take the same amount of time to leaven the dough. Yeasts don't read. As long as you watch the dough and not the clock it doesn't matter. Choose one way that makes sense to you the most and over time you'll get a good idea of what to expect. 

GlennM's picture

I have  adapted yeast recipes and I usually just use a 100 gr or so of starter and remove 50 gr each water and flour from the original ingredients