Member November was kind enough to add another tool to his collection of tools at http://foodsim.unclesalmon.com/.
The tool is called a Hydration Calculator and can be accessed via the Tool Selection pull-down menu at the top, left of the above page. The Hydration Calculator is intended to be used where the rated absorption value of a given flour is not specified by the miller. Most millers do not give that value, although some will provide it upon specific request.
The Hydration Calculator calculates the hydration absorption value of a given flour based on its protein content, dietary fiber content and its moisture content, all measured as percents. Usually these values are given most accurately in the specs of a given flour although the fiber content will usually have to be calculated based on information provided in the specs (typically x grams of Dietary Fiber in a 100-gram sample). Most flours at the millerís have a moisture content of around 14%. However, that value can vary, and usually will once the flour enters the distribution system and is held in storage pending delivery to end users.
An example of a typical spec sheet from which the above information can be ascertained is this one for the All Trumps high-gluten flour from General Mills: http://www.gmflour.com/gmflour/Flour_SpecSheet/ALL%20TRUMPS%20BL%20BR%20ENR%20MT.pdf.
Similar specs for King Arthur professional flours can be seen at http://www.kingarthurflour.com/professional/nutritional-analysis-bakery-flour.html.
An added, but optional, feature of the Hydration Calculator is the ability to take into account the atmospheric moisture (from humidity). The entries for this adjustment are the temperature and relative humidity.
EDIT (4/15/14): For the most recent link to the GM All Trumps flours, see http://www.professionalbakingsolutions.com/product/all-trumps-flour-bromated-enriched-malted-50-lb/50121000