On Font Weight

On Font Weight

1. Example: Lucida Basic font weights. 

Lucida Basic font weight names combine traditional weight names with CSS font-weight numbers. 

The combination of a name + number specifies weights within each Lucida style and also coordinates weights and names between different Lucida families.  

Names like “UltraThin”, “Thin”, “Normal”, and “Black” suggest the visual impression of each weight. Corresponding CSS numbers, 100, 200, 400, and 800, respectively, indicate that each weight in the list is twice as dark as the previous one. 

Other progressions are also definable in this naming method. For example, in the series of Normal (400), Bold (600), and ExtraBlack (900), each successive weight is 1.5 times as dark as the previous one. 

The many gradations of weight in Lucida allow a typographer or graphic designer to choose different kinds of weight progressions for different contexts, different printing methods, different display methods, from ebooks to display screens of different resolutions. 

This table shows the series of weight names and numerical designations




gray %

stem : x-ht





1 : 22





1 : 14.6





1 : 11





1 : 8.8





1 : 7.3





1 : 6.3





1 : 5.9





1 : 5.5





1 : 5.2





1 : 4.9





1 : 4.4





1 : 4.0





1 : 3.7





1 : 3.4





1 : 3.2





1 : 2.8





1 . 2.5





1 : 2.3






In this naming system, when several weights in one style "suite" are installed, they will usually sort by relative weight, so users can see an orderly gamut of weights and choose a desired weight more easily.

Font Weight Waterfall 2


Gray tone of text. The ratio of the thickness of vertical stems in letters like ‘l’ to its font x-height is a way that type designers measure relative weights. In Lucida Lite (Light) weight, the x-height is 7.3 times the vertical stem thickness. In Lucida normal weight, the x-height is 5.5 times the vertical stem thickness. In Lucida bold, the x-height is 3.7 times the vertical stem thickness. As weight goes up, the stem/x-height ratio goes down. This method is a good rule-of-thumb, but the bolder weights are not as visually bold as the number indicate.

A more accurate way to indicate visual weight is to measure actual ink coverage of each weight, or, for modern digital devices, the percentage of black pixels in the total area of the typeface body when the font is set solid, that is, with no extra leading or inter-line spacing. This may be more difficult to measure, but gives a more precise estimation of the graphical facts. A third method, which typographers have used for five hundred years, is to estimate weight by eye and use a name descriptive enough to convey the visual impression. That is how we get names like “light”, “bold”, and “black” to denote what are essentially all tones of gray. 

CSS # weight

Standard CSS weight steps are multiples of 100, including 200, 300, 400, 500, and so on up to 900. For some usages, however, particularly in body text, finer increments are needed to fine-tune tone and readability. Therefore, several Lucida weight steps are offered in finer increments: 150, 250, 350, 375, 425, 450, 550, 650, 999 (this last is really 1,000, but some systems and applications don’t recognize four digit CSS weight numbers.

Why do the Lucida fonts offer more weight gradations?

To allow UI designers, graphic designers, and typographers to tune text and display tones and readability in a wide range of contexts. By choosing from among fine gradations of light and dark weights, a designer can adjust users’ perceptions of text. The goal is not “thin” or “fat” typography but readable typography. 

Extremes. Ultrathin (100) on the light end and UltraBlack (999) on the dark end are the current extremes of the Lucida weight gamut. Maximum weight is ten times minimum weight, offering a dramatic range of expressiveness, from fashionably thin to powerfully bold. 

Main text. Lucida fonts offer finely graded weights for main text, also called running text or body text in a normal reading range. The central weights are Book (350), Text (375), Normal (400), Thick (425), and ExtraThick (450) weights. These subtle gradations enable designers to fine-tune the tone of text in different technical and expressive contexts, for different polarities (black on white versus white on black), colors, and backgrounds, and for different resolutions and technologies of screen displays as well as different printing technologies and paper qualities. The visual impact of a typeface can vary substantially in different contexts. For instance, text in reverse polarity, dropped out of a black or colored background, is more effective if its weight is slightly darker than the weight in black on weight. The fine gradations of Lucida weights permits subtle adjustments.

CSS # versus Pixel %. Weight increments measured by stem to x-height ratios, as expressed in the Lucida CSS weight numbers, are not quite the same as increments expressed by pixel counts. In the  CSS weight numeration of Lucida Sans, the Lite (Light) weight of 300 is 75% of the Normal weight of 400, and the Bold weight of 600 is 150% darker than the normal weight, while the Black weight 800 is 200% (twice) the weight of Normal 400. All very exact. 

However, tonal values measured as pixel percentages show a lesser weight progression. Lucida Lite (Light) weight is roughly 75% of the Normal weight, but the Bold weight is only 132% darker than the normal weight, and the Black weight is only 158% darker than the Normal weight, not 200%. 

Why the difference between the two methods of measure? Because the x-height/stem ratio doesn’t take into account other particularities of type design, including white areas above the x-line and below the base-line, x-height, letter widths, or spaces inside and surrounding the letters. In many type designs, bold weights are somewhat wider than normal weights, thus reducing the emboldening effect of increased stem thicknesses. 

Perception of weight. The final perception of a type design is the image in the mind of the reader, as Adrian Frutiger once said. And so it is with type weight, too. Numbers are essential in practical typography, but ultimately the typographic designer’s goal is to create an image in the mind of the reader, and that is still a difficult and mysterious task. That is why experienced and altruistic typographers are needed to assess the visual impressions of typographic compositions. To envision the experience of the reader and estimate the legibility of text, designers are not always right, nor are weight calculation invariably accurate, but designers and engineers must do their best for readers. As renowned Swiss typography teacher Emil Ruder wrote nearly 50 years ago: “Typography has one plain duty before it, and that is to convey information in writing.” And he wrote this warning: “There is a standing temptation for the typographer to use his type primarily as a tone of grey and thus to allot it a purely aesthetic and decorative role. It is a sign of immaturity to use a grey surface or a grey tone as a basis for a design into which the typography has to fit as best it can.”  

2. A Short History of Type Weights

Differences in typeface weight have been recognized and named by printers and typographers for over five centuries. In English typographic terminology, the earliest weight distinction was between the gothic styles called “black-letter” (or “black letter”, “blackletter”) used in early English printing by William Caxton, compared to the roman style, developed in Italy, particularly by Nicolas Jenson in Venice 147-1480, which early English printers called “white-letter” (or “white letter”). Some roman types were slightly lighter or darker than others, and some blackletter types slightly lighter or darker than others, but by and large, blackletters were darker than white-letters- more ink on the page. However, printers’ choices between gothic or roman, blackletter or white-letter, were not motivated by weight but by style. 

For cultural reasons, principally the intellectual and artistic hegemony of Italian Renaissance typographic fashion, roman replaced gothic in several countries over two centuries: in Italy by the late 15th century; in France by the early to-mid 16th century; and in England by the late 16th century, and in the Low Countries, Belgium and Holland, at about the same time as in England, or not long after (except for beer :-).  

Today, most readers in the Americas and Europe are accustomed to roman types. Most readers of roman would say it is more legible than gothic, yet gothic remained popular in German speaking countries and regions until the 20th century. Gothic types have survived and in many cases have thrived in several contexts, particularly in beer labels and signs in Flemish, Dutch, and German-speaking countries, and also in Mexico. During the Christmas holiday season, typography in English-speaking countries goes gothic and blackletter, when Old English textura and other styles of English blackletter, like the Burgundian Bâtarde used by Caxton, make their annual comeback. From Thanksgiving to New Year’s day in America, blackletter becomes surprisingly legible to roman type readers. God rest you merry, Gentlemen. 

In the 19th century, as the Industrial Revolution gained steam in England, new uses arose for typography in the marketing and advertising of manufactured goods. Typefounders responded by founding more faces for “display” typography, including advertising, posters, handbills, labeling, and ephemera. Among the new promotional type styles were roman faces of heavier weight, surpassing the old gothic blackletters in darkness but still roman in structure. In the vanguard were the so-called “Fat Faces”, which had pronounced thick-thin contrast like Bodoni or Didot designs on steroids. Then came heavy weights with slab-serif faces, the “Antiques” and “Egyptians”, nearly monotonic in stroke thicknesses. Also there were heavy weights of sans-serifs, structurally more like slab-serif faces lacking serifs than roman book faces with the serifs cut off. Related to the Egyptians was a seriffed style called “Ionic”, which had bracketed serifs and a little more contrast between thick and thin than the Egyptians. Following Ionic, the first “Clarendon” typefaces was released in 1845. It was heavy, like many slab-serif faces, but its serifs had bracketing, like Ionic. Clarendon faces began to be used with normal weight roman text faces for headings, emphasis, and other distinctions from the roman text faces. In the early 20th century, typefounders began to integrate bold weights into families of normal weight romans and italics. The Cheltenham and Century families by Morris Fuller Benton for American Typefounders are notable examples. 

By mid-20th century, most new text type families included at least one roman bold weight, and by the late 20th century, most new type families, as well as revivals of older classic faces like Garamond or Baskerville, included two or more bold weights, with names like “semi-bold” and “bold”, or “bold and extra-bold”, with italics of matching weight. In the 21st century, new typeface families often have four or more weight gradations. 

Typeface weight names

Typeface weights have mostly been named on the basis of subjective impression, using metaphorical words like “normal, “semi-bold”, “demibold”, “bold”, “extra-bold”, “heavy”, “black”, and so on. Names like these give an ordinal sense of boldness within a type family. Intuitively, “bold” is darker than “semi-bold”, and “extra-bold” is darker than “bold”. However, even after a century of naming bold weights, there is still no standardization between type families, such that the bold of one family will be the same weight as the bold of another family. The “”demibold” of one font family could be heavier than the “bold” of another family. Or not.

Twentieth century German typographic nomenclature included several named weight gradations, including “mager” (thin), “leicht” (light), “buch” (book [weight]), “normal" (normal), “stark” (strong), “kräftig" (hefty), "viertelfett" (quarter-bold), "halbfett" (half-bold), "dreiviertelfett" (three-quarter-bold), "fett" (bold), and “extrafett” (extra bold). Not all of these were used within a given family. As with English type weight names, there was no standard of use of the German weight names between families. These were, and still are, impressionistic, not numerically calibrated weights. 

Fat. The German type weight terms were borrowed from common items, especially edibles and particularly dairy products. “Dreiviertelfett” in German is used of margarine, cheese, and other items containing fat or weight, and also of typefaces with visual weight (e.g. Venus, Folio, Futura. Viertelfett was used of cheese, margarine, and typefaces (e.g. Helvetica). Halbfett also of cheese, margarine, typefaces (e.g. Helvetica, Neuzeit, Optima, Palatino, etc.). Extrafett could describe creams as well as typefaces (e.g. Syntax, Folio, Helvetica, etc.).

In traditional French typographic nomenclature, weight locutions are similar. “Graisse”, meaning “fatness” in general, is equivalent to English “weight” in type terms, and the weight gamut includes several terms based on the adjective “gras” for fat: “maigre” (thin), “normal” (normal), “demi-gras” (demibold), “gras” (bold), “extra-gras” (extra bold). There appears to be some shifting in recent years, so perhaps our French colleagues will let us know the latest. 

It may seem odd to equate the amount of black in a typeface with the amount of fat in a cheese, but once we take into account traditional printers’ anthropomorphic terminology in talking about a type “face” or “body”, then the metaphor between “weight” on a type and weight on a person seems natural.

But, typeface weight is not necessarily based on fat. In Italian, from which we get wonderful terms of art like “chiaroscuro”, typographic weight names denoted grades of light and dark, like “chiaro” (light), “neretto” (bold), “nero” (black), “nerissimo” (ultrablack). 

Univers decimal weights. In his Univers typeface family, launched in 1957 and designed for universal use in many countries, Adrian Frutiger broke with traditional weight names, which vary from language to language, and devised a two-digit decimal system of naming for consistency across languages, cultures, and nations. In Univers, light roman weight is designated “45”, normal “55”, bold “65”, black “75”, and extra black “85”. Nearly two decades later, the Frutiger family was launched with the same designation system, adding “95” as ultra black. Linotype launched the Neue Helvetica family using the same system, in which “25” designates ultra light, “35” thin, and “95” black. In Univers Next, launched in 1997, the weight gamut and decimal numbering system were extend with an additional digit, “130” became ultralight, “230” thin, “330” light, “430” basic, “530” medium, “630” bold, “730” heavy, “830” black, and “930” extra black. For typographers accustomed to the earlier two-digit naming, the three-digit system requires some extra learning. Neue Frutiger, launched in 1999, and Frutiger Next in 2000 did not continue the decimal nomenclature. 

Normalcy. There is no standard for “normal” weight, that which would be used for running text in books, magazines, newspapers, or on digital screens of computers, tablets, phones, watches, e-books, automotive displays, and other electronic texts. 

“Normal” weights nonetheless fall into a fairly narrow range. For Latin typefaces, their “black” coverage ranges between 15% to around 22%, as measured by the black area (ink or pixels) of the letters within the white area surrounding and inside the letters at their nominal body size, with no leading or extra line spacing. 

For old-style seriffed book faces like Garamond and Caslon, the black percentage is around 16%, give or take a few percent. For 20th century sans-serifs, such as Helvetica or Lucida, and for recent fonts designed for screen display, which tend to have bigger x-heights and heavier thin strokes, the normal weights tend to be darker, around 20%-22% black, give or take a few percent. Old-style book faces were designed for letterpress printing, which deposits more ink on paper and thickens the image though ink-squash around the edges of characters, so letterpress printed texts are slightly darker than modern outline renderings of the fonts would indicate. Some modern sans-serif faces, which became popular in offset lithographic printing are darker than the classical book faces because their slightly heavier weights were not attenuated by the thinner ink films and slight attenuation of lithographic rendering. 

Depending on imaging technology and anti-aliasing algorithms, typefaces on screen displays may be slightly darkened or lightened. For example, on brightly back-lighted high-resolution digital displays, it may be necessary to darken a typeface slightly in order to make it look more like its printed rendering. When Apple moved to “Retina” displays, which on laptops have resolutions of 220 pixels per inch instead of the old CRT resolutions around 72 pixels per inch, Bigelow & Holmes created a slightly darker Lucida Grande Bold weight for Retina displays. The new bold weight was only 4% darker than the old, but that was enough to restore the apparent degree of “boldness”. 

Boldness. Just as there is no standard for “normal” weight across typeface families, there is no standard for “bold” weight. Within a typeface family, boldness is relative to “normal” weight. As seen in the table above, boldness can be expressed as a percentage of gray tone or as a ratio between stem thicknesses, or as a visual judgment. 

Related to findings in the psychophysics of sensory quantities like physical weight, brightness, or loudness, differences in typeface “boldness” seem to  follow a progression based on a multiplicative factor. For many typefaces, the minimum factor for the difference between normal and bold weight is around 1.3 to 1.5, depending on method of measurement. Measured by ratio of stem thickness to x-height, the minimum step for a noticeably bold weight is a factor around 1.5 times the normal stem/x-height. That is, if the normal weight stem is a unit of 1.0, then the bold is around 1.5 units. The next major step in weight, say between bold and black, is roughly 1.5 times the bold, or between 2.0 times the weight of “normal” to around 2.25 times the normal stem thickness.

Designers may prefer a greater degrees of boldness, to make sure it is noticeably more emphatic than normal, but not so bold that it is distracting in text. 

Using the stem/x-height ratio, Lucida Grande Bold is 1.5 x Lucida Grande regular. Palatino Bold is 1.54 x Palatino normal. Arial Bold is 1.6 times x Arial regular. Times Roman Bold is 1.7 x Times Roman normal. Baskerville Bold is 1.8 x Baskerville normal (depending on version of Baskerville). Verdana Bold is 1.9 x Verdana regular. Microsoft’s ClearType fonts, designed for improved screen display technology, tend to have bold weights between 1.5 to 1.7 times the respective normal weights. 

If we switch from measurements based on stem/x-height ratios to black-to-white coverage based on black/white pixel percentages, measure is a bit more complicated (no pun intended) but gives results in decimal percentages. 

Tonal values measured as pixel percentages show a lesser factor of increase. For example, Lucida Lite (Light) weight is 25% lighter than the Normal weight, in both stem/x-height ratio and in black pixel percentage, but in the progression from normal to blacker weights, the Bold weight is only 28% darker than the normal weight, not 50%, and the Black weight is only 37% darker than the Normal weight, not 100%. The exact percentages are influenced by the structure of the design, the x-height, the details of terminals and serifs, the letter fitting, and other factors determined by type designers. 

Definitely bolder versus just noticeably bolder. As discussed above, weights that are“definitely bolder” than normal weight are around 1.5 times normal to 1.3 times normal, depending on the kind of measurement. What about the “just-noticeable difference” or JND used by psychophysicists? How small a difference in typeface weight is just barely noticeable to users or readers? In a small scale study we found that the just-noticeable weight difference for a lower-case sans serif typeface was approximately 3%. Some subjects didn’t detect that small a difference, but more of them did. This accords fairly well with our industrial experience. When our studio developed a minimally darker “bold” weight of Lucida Grande for Macintosh “Retina” displays, the increased darkness was roughly 4%. The small weight increase was just enough that interface designers could notice and prefer the difference, but not so much that average users noticed anything amiss.

A just-noticeable difference is a percept with little or no contextual meaning, being barely detectable, but a definitely noticeable difference carries semantic weight; it distinguishes one sort of text from another, emphasizes a meaning, denotes a definition, keys a topic, indexes a list or a table. Therefore, typographers and interface designers want that difference to be noticeable. In practical typography, type size is another dimension of noticeability, so when a typographer wants something to be clearly more than definitely different, bigger sizes is compounded with bolder weight. 

In summary: what do we know? 

Do we know what type weight is the ideal “normal”? No. 

Do we know what weight is the ideal “bold”? No. 

Do we know how many weights can be used for all desired shades of authorial meaning while enabling readers to understand all the differences? No.

Do we know which design ideology should be our sole guide? Not hardly, as John Wayne would say. 

All these questions must still be determined by context, experiment, visual judgment, analysis and intuition. Weight numbers definitely help, and they are getting better the more we study them, but so far, they remain at best, signs on the road to understanding, not our destination. 

Bigelow & Holmes


Note: We are grateful to Rolf Rehe for his helpful and amusing comments on the “fett” adjectives in everyday and typographic German.

 © 2015 

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