Slope -  Degrees vs. Percent Rise

Discussion created by aduszak81 on Mar 2, 2011
Latest reply on Aug 11, 2014 by msilveira.ucu
After reading all the information Arc provides on slope I am still left wondering which option to use. If I have a DEM and want to calculate all areas in the DEM that have a 10% or greater slope there are two options, for example:

Slope in Percent the range of values are: 0-440
Slope in Degrees the range of values are: 0-77

In both cases I go to: layer properties, click on symbology, and then the classified option. With in the classified option I click "classify". In both cases I see the range of values mentioned above. If I click on "%" button next to break values it appears to give me the percent of slope based on the extent of my DEM, no matter what the range values of my DEM are, the top number is always 100%. My question is, how do you calculate the true slope, as in, what areas of the DEM are greater than 10%?