# Converting a degree slope raster to a percent slope raster, without a DEM, using raster calculator

I've been given a raster of degree slope which I need to convert to percent slope. As the original DEM is not available and those who provided the raster want me to work with this one, I have to convert the degrees to percent. I've attempted to do this with raster calculator, in ArcMap, with the formula (Tan("Degrees"))*100 but this returns nonsensical values with 9+ digits and positive and negative values.

I imagine this is simple but I am doing something incorrectly. Am I missing something or is the wrong syntax? How do I properly convert a degree slope raster to percent slope raster?

• So a 45° slope is a 50% slope, right? So wouldn't the formula be `percent = (degrees/9.0) * 10.0`? Jul 21, 2021 at 1:47
• @Vince, I think 45 degrees is 100% slope! support.esri.com/en/technical-article/000022558 Jul 21, 2021 at 5:24
• You need Tan(3.141593/180*degrees))*100 Jul 21, 2021 at 6:02
• @fatih_dur Doh! Maybe I shouldn't comment while sleepy. Jul 21, 2021 at 14:13
• @FelixIP Thank you! Jul 22, 2021 at 22:06