Two Excel Tools for Sourdough
Two new tools:
Sourdough Spreadsheet 
Sourdough Rye Spreadsheet 
Lately, I've been playing around with my sourdough quite a bit. In particular, I've started keeping a very small amount of starter in the fridge -- about 30 grams or so -- and then building the starter I need from just few grams of "mother" starter over several builds or stages.
Doing the math is a pain. Especially when you're not only mucking about with builds, but also playing around with how much pre-fermented flour you want to use: 20% vs 30% makes a difference in terms of flavor and length of rise.
And then, if you get really nuts, you can start playing around with the Detmold three-stage process for making hearty rye breads, a fairly complicated arrangement that drastically changes how much flour you add and the hydration of each stage.
I got tired of searching for scratch pads and pencils to do all the math required to figure out how much flour I needed and when. So I build these two spreadsheets.
The first is for plain sourdough. Floyd was kind enough to upload it for your downloading pleasure HERE .
If you're using volumetric measurements (cups), I'm afraid this won't be much use to you. There's already a ton of variation in the weight of one cup (In The Laurel's Kitchen Bread Book, for example, a cup is roughly 5.25 ounces! 3 cups = 1 pound!), and with sourdough starter, all bets are off due to all the pretty bubbles.
Any generic weight units will do, so long as they're all the same. Grams are easiest, because they're more precise. As such, I've set the default for most cells to round off to the nearest whole number. But if you'd like to change the defaults to enable decimals so you can use ounces, I'll be glad to show you how to do it.
A few points:
The second spreadsheet is for rye breads, and it's almost exactly the same, except that it allows you to determine the percentage of rye you want in your bread. Download it HERE. 
I'm using this spreadsheet to build my first 70% Detmolder rye with whole wheat. Hee hee! I'll post the results next week. Saturday is baking day. Can't wait!
Hope you enjoy these tools and find them useful!