Leaded or Unleaded?

To understand leading (pronounced “ledding”), you must understand where the term comes from. It’s called leading because typesetters used to manually insert metal strips, made of lead, between rows of type. The more leading the typesetter added, the more space that appeared between the lines of type.

Leading is measured from one baseline to the next baseline.

Leading is the space between lines of type. Technically, leading is measured from baseline to baseline. The default leading for body text is approximately 120 percent of the point size of the type. For example, 12-point type would be set with a leading of 14.4 points (written as 12/14.4). The default isn’t always appropriate. If fact, it’s rarely appropriate.

Relying on default leading settings can get you into trouble. Headings, text set in large type, and text set in all caps requires less leading.

It may seem counterintuitive, but often the larger the type, the less leading is required in proportion to the type size. (Huh? That sentence made sense in my head.) For example, text set in 8-point type would require 10 points of leading, but 72-point type might require only 72 points leading, or no additional leading, which is also called “set solid.”

Computer applications vary on how they measure leading. Some word processors like Microsoft Word measure leading as the difference between the type size and line height. For example, such design applications as Adobe InDesign, Adobe Photoshop, and Adobe Illustrator show type set at 12/14 as you might expect as 12-point type on 14-point leading. Word, however, shows type set at 12/14 as 12 points with 2 points of line spacing (which is essentially the same as 12/14). Note that paragraph spacing is different than leading in that paragraph spacing is the space between distinct paragraphs of text.

Deciding how much leading your text requires is not a straightforward process, because, in addition to type size, you must also consider x-height and line length. I can’t offer a formula for determining the amount of line spacing required for comfortable reading; it’s a matter of aesthetics. As you consider the proper line spacing, take the following factors into account:

• Font Size. Normal text of 10 to 12 points is generally set with one to two points of line spacing. Smaller fonts require more line spacing to be legible. Likewise, large heading or display type will likely require less leading in proportion to the text size.
• X-Height. X-height is the distance between the baseline and median of lowercase letters. The larger the x-height, the more leading is required because the reader needs more space to recognize the word shapes.
• Line Length. Longer lines of text require more line space to prevent the eye from reading the same line twice. Lines of 75 characters or more should be double-spaced. Keep your body text between 35 and 70 characters for easy reading.
• All Caps. Type set in all caps requires less leading because there are no descenders hanging below the baseline, and therefore, there is no chance of collisions between the descenders of one line with the ascenders of the following line.

Notice how fine print and disclosure statements commonly ignore these guidelines. Fine print is typically set in 8-point type or smaller, use a typeface with a large x-height, and little or no leading. Breaking with these guidelines makes the text unreadable, and, if you ask me, attorneys do this on purpose because they don’ want anyone to actually read the disclosures. Follow the guidelines I have outlined here when setting the leading for your own text. After all, you want people to actually read it.