jquery.textWidth.js

(function(window, $, undefined) {
  'use strict';
  $.fn.textWidth = function() {
    var $span = $('<span />', {
      text: $(this).text() || $(this).val()
    }).css({
      margin:     0,
      padding:    0,
      width:      'auto',
      font:        $(this).css('font'),
      display:    'inline',
      visibility: 'hidden'
    }).appendTo(document.body);
    var width = $span.width();
    $span.remove();
    return width;
  };
})(this, jQuery);