May 29, 2010 - 1:54pm

## final hydration formula

I'm no math whiz, but I'm trying to figure out my overall hydration, and could use some help with the math.

Let's assume I have 1000g of dough

700g (70% of dough) is at 55% hydration

300g (30% of dough) is at 100% hydration (my starter)

What would my total dough hydration be?

took awhile, heh

Hi AnnaInMD

Thanks! My question is how did you figure it out?

I ended up building a spreadsheet to enable me to do similar calculations. Really what I was looking for was a way to determine overall hydration when you are using a range of pre-ferments (like firm sourrdough starter, scrap dough, biga, poolish, etc)

It looks like this:

To use it:

First, I type in all your bakers percentages in Column B

Next, I enter initial flour weight in yellow box in Column D

Then, I enter hydration percentages for each starter in the "Hydration" column (Column C)

For each starter, my spreadsheet calculates flour + water amounts to create that hydration percentage.

I total the flours in the dough & starters ("Flour Total" in pink), as well as the liquids ("Water Total" in blue)

Water Total / Flour Total = Overall Hydration (pictured in green box)

Yay!

Hope this helps someone else that's feeling as math-challenged as I am right now :) And please let me know if my math is wrong.

700(.55) + 300(1.00) = 1000X

385 + 300 = 1000X

685/1000 = X

68.5 = X

:)

It doesn't take algebra, just grade school math:

.70(55) + .30(100) = 68.5

Unless my understanding of this is way off, I show the final hydration should be about 66%. OK, How to get there? As follows.

Start with your two known amounts, Starter (300 g of 100%) and rest of dough (700g at 55%). SO total dough is 1000g at x% hydration.

First, the starter: A = flour, B = water. With 100% hydration, A=B.

So 2 A = 300 g. A = 150 g flour; B = 150 g water.

Second, the rest of the dough.

B + A = 700 g.

B (water) = 55% A (flour).

So A + .55A = 700 g. 1.55 A = 700. A = 700/1.55. = 452 g.

B = 700 - 452 = 248 g

As a proof, divide 248 by 452, getting 54.8% (close enough)

Now add the water: 248 + 150 = 398

And the flour: 452 + 150 = 602

Adding these gives you the final dough of 1000 g

For the final hydration, divide the water (398) by the flour (602) and get 66%, unless I goofed somewhere along the line. It would be nice to have a spreadsheet program to figure this out, and if I did it on a regular basis, I would look into one, but the challenge of figuring ir out is part of the Fun (?), no?

David G

Hi Daisy_A,

Decide on your final desired hydration.

Look at your starters, soakers, etc and calculate how much water they account for.

Take that away from your final hydration figure.

The figure you are left with is the amount of water still needed to give you the correct hydration in your overall dough formula.

Best wishes

Andy

I'm not trying to push my spreadsheets. I made them for my use, and they serve me well. However, on the ocassions when I've mentioned them I was getting requests for them.

My spreadsheets begin where Andy suggests: with the amount (weight) of dough I want to make, and what %Hydration I want the final dough to contain.

I also provide for 1 preferment (sourdough starter, biga, poolish, etc.) Its entered by it's weight, and %Hydration also.

The sheets calculate the total flour and water needed to produce the desired dough, and also calculates the contributions of flour and water from the preferment.

Subsequently, you add the flours and liquids you want in the dough. The sheets keep a running total of both the flours and liquids (water, milk, oil, eggs, eggwhites, beer, etc.). You need only to match the running totals to the calculated totals. With a minimum of hand calculation you can account for soakers, and additional preferments by simply calculating their flour and liquid contributions and entering them as such.

It also calculates the needed salt (at 2% of the total flour weight), and provides space for yeast in the preferment (biga, poolish) or dough, and other additions (malt powder, nuts, fruit). The salt is included in the running total dough weight, but not the other additions aren't. They are either too small to be significant, or, my choice was things like nuts, and semi-dried fruits (raisins, craisins, olives,etc.) don't contribute to the dough's strength significantly, nor alter the %Hydration significantly.

The spreadsheets written in Excel (.xls format) are protected, i.e. calculated cells are locked, but there is no password needed to unlock them so you can customize the sheets to your needs if you choose to.

There is also a Starter Calculator Spreadsheet. It does the math for the way I build all my sourdough formula-ready levains from the seed cuture I store in the refrigerator. I use three builds over 24 hours, adjusting the %Hydration in thirds if the formula calls for a starter hydration different from the 100% hydration of the seed culture. My way is a little more labor intensive, and takes about a third longer than the single build most bread book formulas call for, but it's consistent, and produces a very lively formula-ready levain. The link to my blog entry about the three-build method:

http://www.thefreshloaf.com/node/12766/building-formulaready-levain-starter

If you're interested the spreadsheets are available, free, at:

http://glitzandglitterboutique.com/davidg618/spreadsheets.html

David G

David, I went through your spreadsheet and found some weight errors and a couple of other little issues.

Biggest problem was you gram to ounce conversion. Your are using 29.57353, when it should be 28.3495. Why are you using 29.57353?

Thank you. I found the error in the conversion months ago, and thought I had fixed it. I had on my own sheets, but obviously didn't on the web site.

To put it in perspective, the error results in about a 1.5oz error for each kilogram of weight if you start with metric, and about 20g error for each pound of weight if you begin with English units. Converted formula remain viable, only a little bigger, or smaller. Nonetheless, I apologize for any inconvenience its caused others.

I've removed the web page posted above, rather than correct them.

David G