Working Backwards… Or, Thank Goodness for Formulas!

Once I started getting into more advanced recipes, be they sourdough or straight dough, and especially reading books like Jeffrey Hamelman’s “Bread,” which focus heavily on production, it made me start thinking in terms of yield. That is, how much dough should I produce based on the size (weight) of the loaves I wanted to make.

For months, I kind of flailed around using a kilo of dough for pretty much everything, then dividing it up into equal portions. But frankly, that wasn’t very efficient, and it certainly lend itself to consistency from bake to bake.

Why? Simply because if you tweak anything, it changes the weight of the final dough. For instance, let’s say I always use 1 kilo of flour. If I’m making baguettes, I know that I want my hydration to be 75%. Easy enough, the final dough’s flour and water will weigh 1750g. But what if I wanted to drop the hydration to 65% using the same amount of flour. That weight would drop to 1650g! See what I mean?

So what I needed was a way to calculate the ingredient amounts I’d need based on the final weight of the dough. For instance, if I’m making baguettes, my 20-22 inch baguettes should weight 350g apiece. If I want to make 8 baguettes, then I should produce 8 X 350 or 2800g of dough. That’s all well and good, but how do I calculate how much flour, water, salt, and yeast I’d need? This is where the baker’s formula comes into play.

Basic Calculation

Let’s take a simple straight dough baguette formula. In Hamelman’s book, the overall formula would look something like this:

Flour 100%
Water 76%
Salt 1.8%
Yeast 0.25%
Total: 178.05%

When I first saw a formula listed like this, I have to admit that I was totally confused about the number that added all the percentages together. What I later found out is that number is the key to calculating the amount of flour in a recipe based on the final weight of the dough! You simply divide the final dough weight by that number, and you get the total flour in the recipe!

So taking my need for 2800g of dough, the flour I’d need would be 2800 / 1.7805 which calculates to about 1573g, rounded-up. From there, it’s easy to calculate the water, salt, and yeast.

Factoring in a Preferment

A mistake that I used to make and what I see in some books, a lot of blogs, and forum posts is treating a preferment (starter, levain, poolish, biga, etc.) as an ingredient. For instance, saying to use 10% starter. A preferment is simply not an ingredient. It’s a dough development stage; that is, it is part of the overall dough formula and thus the weight of its constituent contents is what’s meaningful, not the preferment itself.

Why is this important? Think about it this way: Let’s take the 1573g grams of flour that I’d need to make my baguettes, for example. 10% of that would be 157g. But if we add 10% of that to the recipe, treating the preferment as an ingredient, we’ll completely throw off our weights. Remember, we’re after a final weight of 2800. If we add 157g to that, we go up to 2957g. Not good.

Furthermore, different preferments will have different hydration rates. If we use a 200% hydration liquid starter, that’ll completely screw up the hydration that I want to be at 76%; not by much, but enough to make a difference in how the dough performs.

So the better approach to take is to consider the flour content in the preferment as a fraction of the total flour, then subtract the flour and water in the preferment from the overall flour and water to keep the final weight the same. With this method, we ensure that the preferment is truly a fraction of the overall dough and not an added ingredient.

The spreadsheet below is something I put together to help me calculate my ingredient amounts for pretty much any kind of bread that I make. I’ve included various other ingredients that I might use. It all goes into the calculation. It’s also available on Google Spreadsheets. Just copy all and paste it into a new sheet.

This has become an invaluable tool for me in calculating exactly what I need to bake all sorts of bread.

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