The State Department’s decision to stop using the Calibri typeface in favor of Times New Roman shook one community far removed from the workings of government: type designers.

“I love it when, once in a while, typefaces come up to the top of the pile in the media news — that doesn’t happen so often,” said Sofie Beier, a type designer and professor at the Royal Danish Academy.

The governmental order was written in Times New Roman, which the State Department had used from 2004 until it switched to Calibri in 2023.

“I wonder if it’s all a bit of a distraction from what the State Department is actually doing, rather than the font they’re doing it in,” said Tobias Frere-Jones, a type designer known for Gotham, Interstate and other ubiquitous typefaces. “But it is an opportunity to talk about what makes things legible.”

Legibility

The legibility of a typeface is “mostly related to how quickly you can read an individual letter,” said Ms. Beier. “You could also call it the clarity of the letter shapes.”

Type designers have rules of thumb about increasing legibility, many of which have been backed up by studies.

Times New Roman is a serif typeface, with small projections that mimic formal handwriting. Calibri is a sans serif, meaning “without serifs.” One study found that “the presence or absence of serifs had no effect on word recognition.”

A higher x-height (the height of a lowercase “x”) and its relationship to ascending and descending letters like “f” and “y” can increase the perceived size of a font and its legibility.

A lower crossbar on the “e” — the most frequently used letter in English — can prevent the top of the “e” from appearing to collapse at small sizes.

More open apertures, the gaps in letters like “c” and “s” and “e,” can reduce the brain’s tendency to close breaks in a nearly continuous shape.

A higher stroke contrast might reduce word recognition in some contexts. Serif fonts, like Times New Roman, tend to have more contrast between their thick and thin lines than sans serif fonts.

“All these different aspects of the letters or the typefaces, they interact,” said Ms. Beier. Typeface design involves thousands of small decisions, all of which contribute to legibility.

Lucas de Groot, the Dutch type designer who created Calibri, first heard about the State Department news when a colleague posted it in Slack. “Then the phone started ringing, and it hasn’t stopped,” he said.

“The Calibri design was based on my experience,” he said. “Most of the design process is not that scientific.” That includes determining proportions for the x-height and other features. “I think it’s much more important how the stuff is perceived. And that’s something that I do from the stomach,” he said.

A classical serif typeface like Times New Roman can look great, Mr. de Groot said, “but of course it needs a lot of work to make it look great. And Times New Roman is possibly the worst choice to trying to achieve that.”

Readability

Beyond letter shape and design, readability might be more important for matters of State.

“Readability is about comprehension and speed, and not about ‘Do you recognize this letter?’ ” said Sam Berlow, one of the founders of The Readability Consortium, which studies digital reading behavior. “Overall, the research time after time says Times New Roman is not a great performer compared to Georgia, Verdana, Helvetica or even Arial.”

When reading long-form text, the eye shifts across written lines in rapid movements, pausing briefly at points of interest. The design of a typeface and the context in which it appears can speed or slow this process.

“There’s a sweet spot between speed and comprehension. If you’re moving too fast, your comprehension’s going to be lower,” said Mr. Berlow. “There are fonts that are very, very fast and easy to read, but comprehension is very low on them. For instance, Montserrat.”

Calibri has generous letter spacing, which can help readers with reduced vision, while Times New Roman’s many serifs tend to intrude on its relatively tighter spacing.

“There is a sort of conventional wisdom that serifs make things easier to read in long-form text. I used to believe that. I don’t really anymore,” Mr. Frere-Jones said. “I think the more important aspect is the proportion of the letters and the amount of space in between them. And in that respect, Calibri does quite well in text and especially text on a screen, which I suspect was part of the previous decision to switch.”

From Paper to Screen

The State Department specifies fonts for paper and print, but those documents will be composed and read on screens. Times New Roman, which was first digitized for computer screens in the 1980s, has notable limitations compared to Calibri.

“Times New Roman doesn’t fare very well on a screen. It’s too delicate to survive on that pixel grid, all those fine serifs,” said Mr. Frere-Jones.

A comparison of Calibri and Times New Roman on a typical computer screen. Lucas de Groot

“And it’s not surprising that it doesn’t fare so well on a screen because it was designed in the early part of the 20th century. No one was working on a screen,” said Mr. Frere-Jones. “So it’s a bit like driving around in a Model T and wondering why you can’t go so fast.”

Accessibility

The State Department’s order noted that Calibri in a 15-point size had been “recommended as an accessibility best practice” during the Biden administration, and described the change as “yet another wasteful D.E.I.A. program,” referring to the acronym for diversity, equity, inclusion and accessibility.

“But accessibility is not one thing that you do and then that box is ticked. When it comes to reading, it’s so many different things,” said Ms. Beier. “If you’re thinking about accessibility and you mean it, then you talk about people of different ages, typically. You have people with different eyesight, you have people with cognitive issues — that could be dyslexia, or difficulties with concentration.”

“It’s difficult to say one typeface definitely helps with accessibility,” she added. “But when we’re talking about these two specific typefaces, I would definitely say that Calibri meets the needs of accessibility more than Times New Roman.”

Government Typefaces

“Serif typefaces are generally perceived to connote tradition, formality and ceremony,” the State Department’s directive argued. “These typefaces are used by the White House, the Supreme Court of the United States, and many state and federal government entities.”

The Supreme Court does use a serif — it issues opinions in the Century Schoolbook typeface, and its Rule 33(1)(B) specifies that documents filed with the Court “shall be typeset in Century family (e. g., Century Expanded, New Century Schoolbook, or Century Schoolbook) 12-point type.”

Recent administrations have tended to choose both a prominent serif and a prominent sans. The Biden administration picked the modern typefaces Mercury and Decimal from Hoefler&Co., while the second Trump administration switched to Instrument Serif and Instrument Sans, free typefaces from Google Fonts.

A recent exception was a new sign for the Oval Office, in raised gold, which appears to be a thickened version of Shelley Script.

A new sign in the White House, seen on Thursday. Doug Mills/The New York Times

The State Department’s order also touched on typographic personality and harmony when it stated, “Compared to serif typefaces, Calibri is informal. When used in official correspondence, Calibri clashes with the formal font of the Department’s letterhead.”

“I think it’s right that Times New Roman is more traditional, or you could say classic. It speaks to an older audience than Calibri does,” said Ms. Beier. “Younger readers typically read more on screen. They read more on their phones, which is where you typically see the sans serif typefaces.”

“I think there is enough evidence that says that serif fonts are taken more seriously than sans serif fonts in printed material. There’s a sort of an authority that hangs on a serif font because of its place in newspapers,” said Mr. Berlow.

“The serif clearly has so much authority built in, which is interesting because it’s just an ornamentation on the letters, and it has so much power,” said Ms. Beier. “We’re not ready to give that up to the sans serif yet.”

This is not the first time that Calibri has become intertwined with politics.

“The daughter of the [prime] minister of Pakistan owned some houses, and she faked a contract,” said Mr. de Groot. “And then somebody found out that the Calibri that she used for these contracts was not available yet at the time the contracts were signed, so the Prime Minister had to step down. That was the ‘Calibrigate.’ That was fun. I got a few phone calls.”

Matthew Butterick, a designer and lawyer who wrote a brief history of Times New Roman, was one of several designers who declined to comment on the recent font news. But he offered a perspective on both typefaces in his book, Typography for Lawyers: “Calibri works well on screen. But in print, its rounded corners make body text look soft.” He added, “It’s not that Times New Roman is a bad font. It’s just that you can and should do better.”