The point of point sizes

Tips

If you use music notation software — or Microsoft Word, or any software where you need to edit text, for that matter — you will very quickly encounter the concept of point size.

12 pt Calibri is the default size and font for a Word document, for example.

Have you ever stopped to consider, though, what point size actually means? And, since we’re talking about music notation software here, why it seems that Sibelius, MuseScore, Finale, and Dorico all seem to have different ideas about what size a point is?

What’s the point? Read on.

The point, defined

We won’t belabor the long history and variability of point size here, but you’re very welcome to read further on the topic. Let’s just establish a couple of basic, um, points:

  • Point size refers to the height of the font — not the height of the letter.
  • For digital publishing, for at least the past 30 years or more, 1 point = 1⁄72 of an inch.

That is mostly what you need to know to get started. But let’s explain a bit more:

  • The point size of the font is equal to one “em” in the currently specified font size. For example, in the 12 pt font above, one em = 12 pt.
  • The “em square” is an imaginary space around which a font size is designed. When the point size of a font is specified (e.g., 12 pt), the font’s em square has that side length.
  • “Em” kind of sounds like “M”. One em was traditionally defined as the width of the capital ‘M’ in the current typeface and point size. But that’s not the case (little font pun there) with most fonts these days.
Diagram showing that the width of a capital M is less than an em wide. Proportional to the font used, each box is one em square. The M on the left is in Perpetua (a typeface with relatively narrow characters); the one on the right is in Calisto (with relatively wide characters).

It’s also the case (ahem) that all fonts are not alike with respect to their height, even at the same point size. “Two fonts set at the same point size will appear to be different sizes if one occupies less space on its em,” as put in Butterick’s Practical Typography.

From left to right, all at the same point size: Academico, Century Schoolbook, Helvetica, Palatino, Times New Roman, Minion Pro, Cailbri

Fonts like Times New Roman or Minion Pro occupy less space on their em, which is why they seem shorter and narrower (and they are) even when set at the same point size as other fonts than Century Schoolbook and fonts inspired by them like Academico and Edwin (the default text fonts in Dorico, and MuseScore, respectively).

If you take away nothing else here, know simply that, although there are 72 points to 1 inch, you cannot determine the size of a font by simply looking at it, or even measuring it on a printed page. Sorry!

What’s more, 10 pt in Sibelius doesn’t equal 10 pt in Finale, or 10 pt in Dorico. Sorry again! But I’ll try to help explain that one further, at least.

Point size, staff size, and spaces

Point size is a unit of measurement that can be converted into other units of measurement, as we just illustrated above.

When we refer to staff size, we mean the distance (on a standard five-line music staff) from the top line to the bottom line (or, more precisely, the distance between the midpoint of each of these lines, so the measurement does not vary with staff line thickness).

A staff is comprised of four spaces in between the lines, and so the size of a staff is always four spaces. A space is a relative unit — just like the em — meaning that its size in absolute terms will be dependent upon the size of the item to which it is compared to. For spaces, that’s the staff size; for ems, that’s the point size.

Follow so far?

The space is the fundamental unit of measurement that defines the appearance of all other notational items. It’s so essential that it’s the very first item mentioned by Elaine Gould in her music notation reference Behind Bars, and it can be scaled regardless of the absolute size of the music.

Staff size, in absolute terms, used to be measured in Rastral sizes, so named thanks to the size of the rastrum that the engraver used to draw the staff. These days, staff size can be measured in any standard unit of measurement. In the era of digital music preparation, it is common to measure the staff size in millimeters, and you can do this in any of the music notation software programs.

In other words, it is fairly easy to instruct any of the programs to set up a document with, say, a 7.0 mm staff size, making the space 1.75 mm (7 divided by 4).

This is all well and good when you have a relative unit of measurement (such as the space or the em) and you want to use it with an absolute unit of measurement (such as the millimeter or the point).

But what happens when you have two absolute units of measurement that you need to use in the same place? This is what happens when you work with fonts, which are measured in points (an absolute unit of measurement), and staff sizes, which are also measured in absolute terms, like millimeters, or inches — or even points.

If you take that 7 mm staff that’s using 10 pt text font, and you increase the staff size 10% to 7.7 mm, when you go into the style settings for your music software, nothing has changed — it will still define the text point size as 10 pt. Yet the text scales appropriately on the page — it’s 10% larger.

What’s going on?

It turns out that in order to keep things straight, behind the scenes, each of their programs have a reference staff size against which text is compared.

In Sibelius (and MuseScore) it’s 7.0 mm…

… but in Finale it’s 24 pt, which is exactly 1/3 inch (about 8.47 mm).

In Dorico it’s 20 pt, which works out to the lovely fraction of 5⁄18 inch, or just ever so slightly greater than 7 mm (7.05556 mm).

This means that at those staff sizes, the absolute size of your text will equal the relative size. In other words, 10 pt relative text will appear legitimately as 10 points, if applied to a Finale staff at 8.47 mm, a Sibelius staff staff at 7.0 mm, or a Dorico staff at approximately 7.05 mm.

However, if you have a Finale staff at 7.0 mm, 10 pt relative text will appear smaller, at about 8.3 pt, or only about 83% of the size it would appear in Sibelius or Dorico, because Finale’s default staff is larger.

What does this mean in practice? The larger the reference staff size, the smaller the size of the font will be, relative to the staff.

Here’s what “10 pt” staff text looks like in each of Sibelius, Finale, and Dorico, using the Academico font, with similar music engraving settings:

Sibelius: 10 pt text font relative to 7.0 mm staff
Finale: 10 pt text font relative to 24 pt (0.3333 in, or 8.47 mm) staff
Dorico: 10 pt text font relative to 20 pt (7.0556 mm) staff

These settings are part of the DNA of each program and cannot be changed. It doesn’t matter what staff size you’re actually using in the document; a 10 pt font size in Sibelius will only actually be 10 pt if it’s used on a 7.0 mm staff.

Unless…

Fixing the absolute size

So far, we’ve been talking about text in music that appears relative to the staff. This applies to most text “within” the music. You’ll find this in technique text, staff expressions, dynamics, and lyrics, as well as some less obvious places like fingering, chord symbols, and tuplet numerals.

But there are other uses for text in music, of course. There’s “system” text, like tempo text and rehearsal letters, and “page” text, like titles and page numbers.

Each of these things are called something a little different in each program, but generally, you wouldn’t want your system text to vary with the staff size — you’d want it to be large enough to read in a conductor score regardless of how small the staff size is, but not too large in a part. And page text should rarely, if ever, vary depending upon the staff size.

That’s where “fixed” or “absolute” sizes come into play. This has the effect of having the text point size break free of being subservient to the staff size, so that you know that 10 pt = 10 pt = 10 pt, in each program, and on your printed page (assuming you print at 100%).

That’s what this does in Sibelius:

Or in Finale:

Or here in Finale:

 

Or in Dorico:

Further reading

If you didn’t get the “point” yet, that’s OK. There is a “font” of knowledge here.

Some of this material is in another Scoring Notes post: “Spaces and the units of measurement for music notation“, where we talk about other elements of music notation like staff lines, stems, and barlines.

There’s also another post, from 2014 (before Dorico arrived on the scene), called “Making Finale’s output look more like Sibelius (and vice versa)“, which is helpful.

And there’s this post, “Working with page numbers in Sibelius“, which goes deeply into how page numbers work in Sibelius, but there is a bit about absolute sizes there, and how to change the setting.

Comments

  1. Jason Loffredo

    Excellent information. Interesting to see how Sibelius and Dorico handle this. Incidentally, I have a great video on Conquering Finale that covers Fixed versus non-Fixed font sizes in Finale. Check it out here: https://youtu.be/Iz5sMwe6nxg

    1. Philip Rothman

      Thanks, Jason! Eventually we will get to “tackling the text tool” around here!

  2. ENRIQUE SANCHEZ

    OH, my goodness! In the back of my mind, FONT sizes were always the great conundrum that my less -than -mathematical-mind couldn’t wrap around my brain! Thank you for this fascinating explanation and for finally organizing the mush that polluted my thoughts into a more coherent whole!

    1. Philip Rothman

      Thanks, Enrique! Happy to contribute to pollution reduction efforts, in whatever form they may take.

  3. Jay Anthony Gach

    Yeah Phillip this is critical stuff for us composers who still have to do our own orchestra parts so as not to burn up all the commissioning fee hiring out the parts. Apropos this above post/tip, I for one still have problems with Sibelius font sizes in full scores being toooooo large in the parts (op cit your example of “size in score” relative and absolute to 7mm staff) and end up making a separate “part score” where tempo markings, staff text, etc are in much smaller font sizes so they appear correctly sized in the parts. IDK that would be sure be a great subject for one of your tip/postings tho’ perhaps too big an ask. Again, cheers and thanks for this informative posting.

    1. Philip Rothman

      Thanks Jay! Did you know that in Sibelius you can choose to size text separately for the score and parts, for each text style? It’s actually in the image there. Or were you talking about something else?

  4. Michael Philcox

    At the beginning, you say, “point size refers to the height of the font—not the height of the letter” and later, “the ’em square’ is an imaginary space around which a font size is designed”. However, the attached diagram of capital M’s in Perpetua and Calisto fonts do not approach either the sides or top and bottom of their “em squares”. Am I correct in assuming then that it is wholly a font designer’s choice how much of the “em square” he or she wants to use in drawing the font characters?

    1. Philip Rothman

      Yep, that’s exactly right. Obviously it doesn’t mean that there will be empty space between the letters, though.

      Butterick’s Practical Typography has more explanation here and here.

      1. Michael Philcox

        Thanks, Philip. I was confused but at least this particular aspect of font design and nomenclature is now more clear.

  5. Andrei

    You continue to make many fine points in this space, Philip! Thank you!

    1. Philip Rothman

      Thanks, Andrei! I’ve taken note and will make sure to pickup the tab at the bar to thank our staff, who measure up well.

  6. Jacques Bailhé

    Excellent! The.double entendres were fun but also curiously helpful.

    1. Philip Rothman

      Thanks, Jacques! I’m glad you enjoy our humor and that it’s helpful, too.

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