x-Height

The term x-height refers to the height of the lowercase x in a given typeface at any given size. It provides a way of describing the general proportions of any typeface.

Point Size Is Different Than x-Height

The point size of a typeface is basically a measure of its overall height, from the top of the tallest character above the baseline to the longest descender beneath the baseline. However, since, over 95 percent of all Latin letters read are lowercase, with proportions that vary from typeface to typeface, their x-height is an important factor in both legibility and readability. It offers a highly practical way to classify the size of the vast majority of the characters read.

Seemingly similar typefaces may in fact have very different x-height proportions. For example, the lowercase characters in the Gill Sans typeface family are noticeably smaller than those of the ITC Avant Garde Gothic typeface family. The lowercase letters in the Plantin typeface family are considered to have a relatively generous x-height, while those in the Bernhard Modern family are usually considered small.

Large x-Heights

Large x-heights generally make a typeface more visible at any given size. Thus, display faces with very large lowercase characters tend to communicate with clarity and emphasis. Text typefaces that incorporate large x-heights generally do so in an attempt to increase legibility and readability. The Spartan Classified font, which is designed to be legible at very small sizes, has a much larger x-height than the Futura typeface it was patterned after, which was intended for text composition within a normal point-size range.

Small x-Heights

Although a large letter size may be preferable in some scenarios, bigger is not always better. This visibility usually comes at a price. As the x-height increases, the length of the ascenders and descenders decreases. Taken to the extreme, this can reduce character legibility. For this reason, a typeface like Antique Olive, for instance, is fairly difficult to read at small sizes.

Typefaces with large x-heights also take up more real estate than those with small x-heights. For example, in any given measure, about 10 percent more copy can be set using a typeface like Perpetua than one like ITC Legacy Serif. A 10 percent longer book or a line of advertising copy that has to be set 10 percent smaller to fit on a page is a significant outcome to consider.

Typefaces with small x-heights can also save space in another way. If lines of copy are set with no additional line space, the proportionally longer ascenders and descenders of a typeface with a short x-height will create the illusion of more white space between lines of type.

As with most matters typographic, there are few fixed rules regarding the choice of typefaces with various x-heights. Considering the audience, the reading environment, and the typographic application is always an appropriate starting point when choosing typefaces with the right x-height for any given situation.

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• Allan Haley is Director of Words & Letters at Monotype Imaging. Here he is responsible for strategic planning and creative implementation of just about everything related to typeface designs. He is also responsible for editorial content for the company’s type libraries and Web sites.
• Prior to working for Monotype, Mr. Haley was Principal of Resolution, a consulting firm with expertise in fonts, font technology, type and typographic communication. He was also executive vice president of International Typeface Corporation.
• Mr. Haley is ex officio Chairman of the Board of the Society of Typographic Aficionados, and past President of the New York Type Directors Club. He is highly regarded as an educator and is a frequently requested speaker at national computer and design conferences.
• Mr. Haley is also a prolific writer, with five books on type and graphic communication and hundreds of articles for graphic design publications to his credit.