You can change measurement units for the on‑screen rulers and for use in panels and dialog boxes; you can also change these settings at any time and temporarily override the current measurement units as you enter a value. By default, rulers begin measuring from the upper-left corner of a page or spread. You can change this by moving the zero point.

Changing the measurement units doesn’t move guides, grids, and objects, so when ruler tick marks change, they might not line up with objects aligned to the old tick marks.

Rulers in a document window

A.

Labeled tick marks

B.

Major tick marks

C.

Minor tick marks

You can set up different measurement systems for horizontal and vertical rulers. The system you select for the horizontal ruler governs tabs, margins, indents, and other measurements. Each spread has its own vertical ruler; however, all vertical rulers use the same settings you specify in the Units & Increments preferences dialog box.

The default units of measure for the rulers are picas (a pica equals 12 points). However, you can change custom ruler units and control where the major tick marks appear on a ruler. For example, if you change the custom ruler units for the vertical ruler to 12 points, a major ruler increment appears every 12 points (if such display is possible in the current magnification). The tick mark labels include your customized major tick marks, so when the ruler reads 3 in the same example, it marks the third instance of the 12‑point increment, or 36 points.

Vertical ruler using inches (left), and custom 12‑point increments (right)

Setting custom ruler increments in the vertical ruler is useful for lining up a ruler’s major tick marks with a baseline grid.