Get width/height of SVG element

Use the getBBox function:

The SVGGraphicsElement.getBBox() method allows us to determine the coordinates of the smallest rectangle in which the object fits. […]

http://jsfiddle.net/Xkv3X/1/

var bBox = svg1.getBBox();
console.log('XxY', bBox.x + 'x' + bBox.y);
console.log('size', bBox.width + 'x' + bBox.height);