cast off

To cast off is to calculate in advance how many lines of typeset text, or how many pages, will result from a given manuscript or block of copy. The compositor estimates the final length by measuring the characters in the manuscript and applying the width and leading of a specific typeface and point size. This prediction determines whether the text will fit the allocated space, require editing, or need a different type specification.

The traditional method uses a cast-off scale or type gauge. The compositor counts characters in the manuscript (including spaces and punctuation), then multiplies by the average character width for the chosen typeface. The character count is divided by the line length to find total lines; total lines multiplied by the leading gives the depth in inches or picas. Digital typesetting software now calculates this automatically, but the principle remains: predicting final page count before composition begins.

Common pitfalls and variables

Different typefaces occupy different widths at the same point size. A manuscript cast off for 10-point Times may not fit if switched to 10-point Helvetica. Proportional typefaces complicate the estimate because an i is far narrower than an m. Monospace fonts like Courier simplify casting off since every character occupies identical width. Leading also shifts the equation; tighter spacing condenses the page, wider leading extends it.

Casting off matters in imposed work: when a booklet or magazine must divide evenly across signatures, miscalculations force awkward cuts, blank pages, or expensive reprinting. An estimate that is off by even two or three lines may shift a chapter break to an undesirable position. Historical castings-off were often conservative, padding estimates to avoid overruns.

The term reflects the mechanical nature of print production. To "cast off" originally meant to break away or separate; here it means to calculate and set aside the space type will occupy, freeing both designer and compositor to plan the job confidently. In digital workflows, the task is nearly instantaneous, yet the vocabulary persists because the conceptual step remains essential to print planning.