How to draw a circle of radius in meters using canvas.drawCircle() that needs radius in float in android

Question

I have this requirement of drawing two concentric cricles on canvas. The inner one with radius of 300 meters and outer one with radius of 500 meters. Till now i have been able to find the center of the screen with respect to coordinates in lat long. What i am trying to figure out is, how to map the meters to float while using canvas.drawCircle

This is my code for the time being I have two circles with random radii in float 120 and 160.

        int x = ((MapView)mParent).getWidth()/2;
        int y = ((MapView)mParent).getHeight()/2;

        dPointLatLon dLatLon = MapToWorld(x,y );
        System.out.println("LAT " +dLatLon.lat);
        System.out.println("LON " +dLatLon.lon);


        canvas.drawCircle( x, y,120f , mSelectionBrush);
        canvas.drawCircle( x, y,160f , mSelectionBrush);

This is my out put. Can you please guide me to how to use the distance in meters and convert them to fit into canvas.drawCircle.