1. I looked at the font.
2. I expected the 12pt font to have a pitch of 10.
3. The 12pt font has a pitch of 12. I'm on Jammy 22.04 but this applies to the font, so that doesn't matter.

Here's a less pretty version of what I linked above:



Preamble:
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hello folks. i am cheer, your local typewriter nerd, and i am here to explain why ubuntu mono is scaled incorrectly. i was going to write "hold on to your hats" or "buckle up folks" here, but truthfully there is no need: i am probably the only person in the entire world who cares about this.

with that, let's get our shift keys warmed up and dive into the problem. (more like pre-ramble am i right??)

Background:
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Monospaced typespaces originate from typewriters. In the US, typewriters were largely split into two different categories based on Pitch, which is the number of Characters Per Inch (CPI). The 10 pitch fonts were called Pica and the 12 pitch fonts were called Elite.

A common mistake is to assume that Elite is the larger size. It does have the bigger number, but its a measure of CPI, and the size of each character has to decrease to fit more characters within the same amount of space. Therefore, Pica (10CPI) is bigger then Elite (12CPI).

The Very Cool and Fun Part:
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There is a typographic unit of measure known as the pica. It has nothing to do with the Pica font. One pica corresponds to 1/6 of an inch, and can be further broken down into 12 points.

Another thing to note is that— for some reason that I do not know—A Pica font has a 12 point
font size. The same is true of Elite and 10pt font size.

To summarize:

  - Pitch is the amount of characters per inch in a monospaced font
  - Point is a unit of measurement. 12 points equal 1 pica.
  - Pica is a 10 pitch font with a 12pt font size
  - Pica is a unit of measurement equivalent to 12 points
  - Elite is a 12 pitch font with a 10pt font size

See how this might get confusing?

The Problem:
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Many years ago, a great tragedy occurred on September 1X, 20X1. It's a day that I will never forget: September 14, 2011. The Ubuntu Mono beta release. Though not a tragedy in itself, the announcement post contains the following line:

Just like a typewriter there are 12 characters per inch at 12 point.

Weep with me, dear reader, so that I do not have to mourn this blunder alone. It is as though the entire field of typography set the Ubuntu Mono team up for failure—why else would there be twelves and tens and picas and pitches and points aplenty?

While it is a very understandable mistake to make, it unfortunately results in Ubuntu Mono being the only* monospaced font that is sized the way it is.

*out of all the ones i bothered checking, at least.

Conclusion:
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https://user-images.githubusercontent.com/31635100/176266679-7cabc422-ef7b-4b30-bb4a-1e16e849ca0e.png

The thicker grid lines mark 1 inch, which is divided into 10 subsections. All 12pt monospaced fonts but Ubuntu Mono result in one character per box, for a total of 10 characters per inch. While I didn't adjust the grid for the 10pt examples, it is still clear that they have a pitch of 12..

12pt Ubuntu Mono is a 12 pitch font, but it is supposed to be a 10 pitch font. As is, the 12 pitch font is equivalent to any other 10pt monospaced font.

thank you for your time.