Baker’s Math in Action

You’re about to make Vienna bread from The Bread Baker’s Apprentice, when you notice something strange: the pâte fermentée recipe on page 105 nets 16 to 17 ounces; but the Vienna bread recipe only calls for 13 ounces. So, what do you do? Make the full pâte fermentée recipe and throw out the excess? Cut the recipe in half and make do with 8 or so ounces of pâte fermentée?

Neither. You use baker’s math to scale the recipe to 13 ounces. You’ve no doubt noticed the Baker’s Percentage Formula sidebars in Peter Reinhart’s recipes. You may even have read his explanation of the use of baker’s math. But have you ever wondered how to actually go about using baker’s math to scale a recipe?

It’s easier than you think.

Let’s take the pâte fermentée recipe as an example. In baker’s percentages, the recipe is as follows:

  • Bread flour:  100% (remember that the flour will always equal 100%)
  • Salt:  1.9%
  • Instant yeast:  0.55%
  • Water:  65%
  • Total:  167.5% (I know, I know. A total exceeding 100% is maddening; but I didn’t invent baker’s math. I just use it.)

Let’s start with the flour. To figure out how much flour to use, first divide the flour percentage by the total percentage of the recipe:

  • 100/167.5=0.5970

Next, multiply the result by the total amount you want to make, in our case, 13 ounces:

  • 0.5970*13=7.761

The recipe calls for equal amounts of all-purpose and bread flours, so as a final step, divide this amount in half to get 3.88 ounces. (As a final, final step, I rounded this amount to 4 ounces each of all-purpose and bread flours.)

Repeat this process for the remaining ingredients:

  • Salt:  1.9/167.5=0.0113*13=~0.15 ounce
  • Water:  65/167.5=0.3881*13=~5 ounces

And the yeast? To my mind, 0.055 ounce is too small an amount to bother scaling down, so I just used a scant 1/2 teaspoon.

To recap, as long as you know the baker’s percentages, you can scale any recipe to size by dividing the percentage of each ingredient by the total percentage in the recipe, then multiplying by the total amount of dough you want to make.

So, there you have it. Baker’s math in action. Please, try to contain your enthusiasm.


  1. Samuel Stevens said,

    March 22, 2010 at 9:13 pm

    When I first got the book I read the formula’s section over and over and I finally got it. Being the spreadsheet nerd I am I put it all the formulas in a spreadsheet to auto fill for you. You can chose either by total weight or weight by ingredient that you want to bake to and it auto fills all the other ingredients for you. All you have to do is put the baker’s percentage in and it does it all for you. I wish I could somehow share it with all because it makes this math even easier. Of course then you don’t have to think for yourself, but isn’t that what computers are for anyway?

  2. February 28, 2010 at 3:08 pm

    […] requires 10.5 ounces of starter. The starter recipe, on the other hand, yields 39 ounces. Time for baker’s math again. By using 1.9 ounces of starter and 4.3 ounces each of flour and water, I ended up with […]

  3. Natashya said,

    February 9, 2010 at 1:20 pm

    I can understand the concept of baker’s math, but have never taken the step to put it into action – you do it beautifully!

  4. February 9, 2010 at 7:31 am

    Great post! Thanks for the explanation. I’ll be making the Vienna bread soon.

    • gaaarp said,

      February 9, 2010 at 8:31 am

      Let me know how you like it. I loved it, and was glad not to have to waste any preferment.

  5. AnneMarie said,

    February 9, 2010 at 7:08 am

    Phyl, my mother was a high school math teacher. The numbers greater than 100% drive me crazy. But great post explaining the math.

    • gaaarp said,

      February 9, 2010 at 8:31 am

      Thanks. Yeah, the numbers make me nuts, too. The beauty of it is, the first part of the equation in essence recalculates the recipe on a 100% scale. In fact, I often perform the first operation (Ingredient Percentage/Total Percentage) and write the resulting percentage in the margin of the recipe. That way, I can go back to the recipe and easily scale it to any final dough weight that I want.

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