smart-create,
в документации даже пример есть того, что вы просите
http://api.jqueryui.com/draggable/#event-drag
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
#draggable { width: 150px; height: 150px; padding: 0.5em; }
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.4/themes/smoothness/jquery-ui.css">
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.4/jquery-ui.min.js"></script>
<script>
$(function() {
$( "#draggable" ).draggable({ axis: "x",
drag: function( event, ui ) {
$( "#draggable" ).html(ui.offset.left); // ui.position.left
}
});
});
</script>
</head>
<body>
<div id="draggable" class="ui-widget-content">
<p>Drag me around</p>
</div>
</body>
</html>