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?
    – Vince
    Commented Jul 21, 2021 at 1:47
  • 3
    @Vince, I think 45 degrees is 100% slope! support.esri.com/en/technical-article/000022558
    – fatih_dur
    Commented Jul 21, 2021 at 5:24
  • 1
    You need Tan(3.141593/180*degrees))*100
    – FelixIP
    Commented Jul 21, 2021 at 6:02
  • @fatih_dur Doh! Maybe I shouldn't comment while sleepy.
    – Vince
    Commented Jul 21, 2021 at 14:13
  • @FelixIP Thank you!
    – YamCham
    Commented Jul 22, 2021 at 22:06

1 Answer 1


I took @FelixIP's advice and used the formula Tan(3.141593/180*degrees))*100. This correctly converts degree slope raster values to percent slope values.

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