ZBrushCentral

stl to obj converter

Hi, I am quiet new to the 3d sculpting world. Normally I am a professional traditional sculptor trying a new medium. My newses problem is to convert a stl file into an obj that I could load it into my zbrush or sculptris. I have tryed googlesearch and also have downloades a bunch of programs with no sucsess.
Anyone got an idea ?
stl to obj converter ?