How wide is the required left margin on a true legal pad?

The required left margin on a true legal pad is 1.25 inches, or about 3.17 centimeters.

The margin, sometimes called the down line, runs vertically near the left edge of the page. It creates a dedicated space for notes, comments, editing marks, or other annotations separate from the main writing area.

Legal pads are usually bound at the top rather than along the side. They are commonly associated with yellow paper and blue horizontal ruling, but the color is not the defining requirement. The precise left margin is the technical feature that distinguishes a true legal pad from a generic lined writing pad.

A popular story credits Thomas W. Holley of Holyoke, Massachusetts, with developing the legal pad around 1888 by assembling low-cost paper scraps. The yellow format and margin became associated with later development, including a request from a judge for space to add comments.