Create Graphic radius kilometer

[ManuelImedio]

I have a map and need to add a coat that is a circle of radius X KM
The code I have right now is:

graphicsLayer.addGraphic (new Graphic (redlands1, new SimpleMarkerSymbol (Color.argb (82, 100, 0, 0), 20, STYLE.CIRCLE)));

The size is 20 but that does not mean, I do not know the actual size, is there any way?

Thanks

[ManuelImedio]

Solve the problem getting the size of the map dp (mapa.width) and getting the points on the map and calculating the distance in miles between them.

360 dp --- 1000 meters
x           ---  2000 meters