Hydration Percentage + Bakers Formulas

Hydration is the ratio of water (weight in grams) to flour (weight in grams), so the Pane Pugliese recipe described in the blog is 452g of water to 625g flour, which is 452/625x100 = 72.32%

Hydration is a measure of how wet the dough is:
•Stiff & Dry- 58 to 60% water content
•Firm & Tight – 60 to 62%
•Modestly Firm – 62 to 63%
•Malleable – 63 to 64%
•Soft – 64 to 65%
•Slack – 65 to 67%

Peter Reinhart lists these classifications:
•Stiff - 50 to 57% water content (bagel, pretzels)
•Standard - 57 to 65% water content (French and other European style breads)
•Rustic - above 65% water content (ciabatta, pizza, focaccia)

Source: Baker's Percentages and Bread Hydration

Professional bakers express their recipes as formulas. The amount of flour always adds up to 100% and the remaining ingredients are a percentage of the total flour, and it’s always by weight, not volume.

Using the Pane Pugliese recipe:
Flour...625g...100%
Water...452g....72.3%
Salt......9g.....1.5%
Yeast.....4g.....0.64%

Peter Reinhart lists these formulas:
Total Flour Weight = Total Weight / Total Percentage
Total Weight = Ingredient Percentage x Total Flour Weight
Ingredient Percentage = Ingredient Weight / Total Flour Weight x 100

Knowing these formulas allows us to scale recipes up or down according to the size loaf (or loaves) that we are trying to create.

One item that throws off the calculations is the inclusion of pre-ferments such as bigas, poolish, pate fermentee, and sourdough or other starters. I personally think that it is easier to include those in the total percentages.

For example, the original recipe for the Pane Pugliese came from Carol Field's The Italian Baker:
1 1/4 tsp active dry yeast (5g or .50%)
1/4 cup warm water
3 cups water room temperature
200 grams of biga
1000 grams of unbleached AP flour
20 grams of salt (2%)
With water at approximately 230g per cup, the 3.25 cups of water would weigh 747.5g
This would be 74.75% hydration. (note to self: recalc this at 236g per cup)

(here is a nice conversion tool:)
Ingredient Conversion

Then the recipe for 750 grams of biga is:
1/2 tsp active dry yeast (2g or .40%)
1/4 cup warm water (57.5g)
1 1/4 cups + 2 tbsp water room temperature (287.5g+28.5g=316g)
500 grams unbleached AP flour
The total water weight is 373.5g (74.75% - same as the recipe!)
The total ingredient weight is 373.5+500= 873.5
BUT we only need 200g of biga, then
Total Flour Weight = Total Weight / Total Percentage
TFW = 200 / 1.75 (175%) = 114g

Ingredient Weight = Ingredient Percentage x Total Flour Weight
Water = .7475 x 114 = 85g

SOOOoo..
The converted recipe would look like this when you include the flour, water, and yeast from the biga:
Flour 1114g
Water 832g (74.68%)
Salt .. 20g (1.79%)
Yeast .. 7g (.63%)

But this makes 2 large loaves or 3 smaller loaves.
If you set the total flour to 625g, then the recipe easily falls into place.

Here is another source for bakers percentage:
Artisan Bread Baking

Here is some great info on yeast dough:
King Arthur Flour