These docs are for an old release. Info on upgrading to version 2/3
edit doc

aspectRatio 1.3

Determines the width-to-height aspect ratio of the calendar.

Float, default: 1.35

A calendar is a block-level element that fills its entire available width. The calendar’s height, however, is determined by this ratio of width-to-height. (Hint: larger numbers make smaller heights).

The following example will initialize a calendar who’s width is twice its height:

$('#calendar').fullCalendar({
  aspectRatio: 2
});

Setter

You can dynamically set a calendar’s aspectRatio after initialization:

$('#calendar').fullCalendar('option', 'aspectRatio', 1.8);

The setter only works in version 1.4.2 and later.