Finding mouse position on canvas. Is there a better way?

I have a canvas 2000 px wide, which fits the width of the client window.

If I use a mouse event with event.clientX I must calculate the relative position with respect to the window width.

If I use a mouse event with event.clientY I must calculate the relative position with respect to the window width plus offset due to the scrolling of the window.

$(canvas).mousedown(grdown.bind(this));

function grdown(e){

var rect = canvas.getBoundingClientRect();

console.log("clientX   " + (e.clientX * (2000/canvas.width)) + "    clientY   " + ((e.clientY * (2000/canvas.width))-rect.top * (2000/canvas.width)    )    );

}            //          this eventListener is done with jQuery

Is there a simpler way to do this?