When it comes to baking, percentages and amounts are important.  There is a reason recipes specify 1.5 teaspoons of yeast.  That being said, based on your kitchen’s conditions sometimes things might need to be adjusted.  When that happens you need to know what and how to adjust in order to be successful.

Baker’s percentage is a way of expressing the amount of each ingredient in a recipe relative to the amount of flour.  So, if a recipe has 1000 grams of flour, 600 grams water, 30 grams of yeast and 20 grams of salt, the percentages would look as follows…

Ingredient	Amount	Percentage
Flour	1000 g	100%
Water	600 g	60%
Yeast	30 g	3%
Salt	20 g	2%

With a baker’s percentage, flour will always be 100% as it is a way to measure relative proportions.  You may also see the term hydration, which refers to the specific percentage of water.  So, a dough that is 60% hydrated has a 6:10 ratio of water to flour.

If you venture into sourdough, remember that your starter has both water and flour and to include that in your percentages.  For example, the 70% hydration sourdough I made has a baker’s percentage that looks like this…

Ingredient	Amount	Percentage
Flour (Bread and Whole Wheat)	500 g	67%
Flour (Starter)	250 g	33%
Water	275 g	37%
Water (Starter)	250 g	33%
Salt	20 g	2.7%

You’ll notice that the flour (750 g total) still adds up to 100%.  But since I added 500 grams of a starter that is 50% flour, I had to take that into account.  The total amount of water (525 grams) is 70% of the total amount of flour, hence 70% hydration.

So why does this matter?  A few reasons.  First, knowing and understanding percentages makes multiplying recipes much easier (as does using the metric system).  Second, it allows you to adjust a recipe and understand when and why something should be adjusted.  Say you’re making bread in the humid paradise of Tallahassee, Florida.  You are probably going to need 2-3% less water to finish the recipe, whereas you might need more if you pick up and move your kitchen to Arizona.

Lastly, the relative percentage of ingredients helps classify what type of bread you’re making. Bagels are a very stiff and dense dough, around 50-55% hydration.  The light wheat sandwich bread I make on a regular basis runs around 57-60%.  So knowing the baker’s percentage for a recipe and associated hydration can help a lot when troubleshooting a recipe or just creating one on the fly.

I have found this guide from Stella Culinary to be exceptionally helpful.  It also details other ways to classify breads, which is very helpful when trying to improvise.