Untitled

html,
body {
  width:100%;
  height:100%;
}

.half-size
{
   transform:scale(0.5);
  -moz-transform:scale(0.5);
  -webkit-transform:scale(0.5);
}
.quarter-size
{
   transform:scale(0.25);
  -moz-transform:scale(0.25);
  -webkit-transform:scale(0.25);
}

#draggable-element {
  width:100px;
  height:100px;
  background-color:#666;
  color:white;
  padding:10px 12px;
  cursor:move;
  position:relative; /* important (all position that's not `static`) */
  display:block;
}

var selected = null, // Object of the element to be moved
    x_pos = 0, y_pos = 0, // Stores x & y coordinates of the mouse pointer
    x_elem = 0, y_elem = 0; // Stores top, left values (edge) of the element

var elem_height = 0;
var elem_width = 0;

// Will be called when user starts dragging an element
function _drag_init(elem) {
    // Store the object of the element which needs to be moved
    selected = elem;

    var boundingRectangle = selected.getBoundingClientRect();

    y_elem = (selected.offsetHeight - (boundingRectangle.bottom - boundingRectangle.top)) / 2;
    x_elem = (selected.offsetWidth - (boundingRectangle.right - boundingRectangle.left)) / 2

    half_elem_height = (boundingRectangle.bottom - boundingRectangle.top) / 2;
    half_elem_width = (boundingRectangle.right - boundingRectangle.left) /2;

    document.addEventListener('mousemove', _move_elem, false);
    document.addEventListener('mouseup', _destroy, false);
};

// Will be called when user dragging an element
function _move_elem(e)
{
  x_pos = e.clientX;
  y_pos = e.clientY;

  selected.style.left = ((x_pos - x_elem) - half_elem_width) + 'px';
  selected.style.top = ((y_pos - y_elem) - half_elem_height) + 'px';
}
// Destroy the object when we are done and remove event binds
function _destroy() {
  selected = null;
  document.removeEventListener('mousemove', _move_elem);
  document.removeEventListener('mouseup', _destroy);
}

// Bind the functions...
document.getElementById('draggable-element').onmousedown = function () {
    _drag_init(this);
};

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
</head>
<body>
<div id="draggable-element" class='half-size'>Drag me!</div>
</body>
</html>

// Will be called when user dragging an element
function _move_elem(e) {
var el = window.document.body;
var st = window.getComputedStyle(el, null);
var tr = st.getPropertyValue("transform") ;

var values = tr.split('(')[1];
    values = values.split(')')[0];
    values = values.split(',');

var a = values[0];
var b = values[1];
var c = values[2];
var d = values[3];
    x_pos = document.all ? window.event.clientX : e.pageX;
    y_pos = document.all ? window.event.clientY : e.pageY;
    if (selected !== null) {
        selected.style.left = ((x_pos / a) - x_elem) + 'px';
        selected.style.top = ((y_pos /  d) - y_elem) + 'px';
    }
}