Use the Measurements pane of the Preferences dialog box (QuarkXPress/Edit menu) to specify default measuring units for layout rulers and the Measurements palette:

• Use the Horizontal and Vertical drop-down menus to specify the measurement system for the rulers displayed along the top and left of the layout window. Horizontal corresponds to the top ruler; Vertical corresponds to the left ruler.
• Several other aspects of the user interface are affected by these two drop-down menus, including the default X and Y coordinates in the Measurements palette. QuarkXPress automatically converts font size, frame width, leading, and line width to points, regardless of the measurement system you choose.
• Use the Points/Inch field to override the default value of 72 points per inch. QuarkXPress uses the value here as the basis for all point and pica measurements, as well as for all point- and pica-to-inch conversions. The desktop publishing standard for points per inch is 72. However, the traditional typographic standard used on most metal typographic rulers is usually approximately 72.27 or 72.307 points per inch (range = 60 to 80 pt, measurement system = points, smallest increment = .001).
• Use the Ciceros/cm field to specify a ciceros-to-centimeter conversion value different from the standard 2.1967 (range = 2 to 3 c, measurement system = ciceros, smallest increment = .001).
• Print layouts only: Use the Item Coordinates buttons to specify whether the increments of the horizontal ruler repeat from zero for each Page or are continuous across a Spread. This setting determines the coordinates of items displayed in fields. The default option is Page.
• Use the Measurement Units drop-down menu to set the default measurement unit for new layouts.