# Using the same font for numbers in math mode in LaTeX

It really bugs me when numbers are typeset with two different fonts on the same line, say in MS Word if you type 0.01 in the text and then the same in an equation field, they won’t look the same because they use different fonts. For my dissertation (written in LaTeX), I wanted to be sure to avoid this pitfall. Unfortunately, it is rather more complicated than it seems on the face. First, you must use XeLaTeX (which I am). Second, the packages `fontspec` and `unicode-math` are necessary. `fontspec` lets you set the main body font, while `unicode-math` lets you control the fonts used in math environments (between `\$`, or in an equation environment, etc.). However, by default, `unicode-math` will typeset all of the numbers in whatever font you choose with that package so the default must be changed. For instance, in my dissertation, I have

```\usepackage{fontspec}
\setmainfont[Ligatures=TeX]{Times New Roman}

\usepackage{unicode-math}
\unimathsetup{math-style=TeX}
\setmathfont[range=\mathup/{num}]{Times New Roman}
\setmathfont[range=\mathit/{greek,Greek,latin,Latin}]{Cambria Math}
\setmathfont[range=\mathup/{greek,Greek,latin,Latin}]{Cambria Math}
\setmathfont[range={"2212,"002B,"003D,"0028,"0029,"005B,
"005D,"221A,"2211,"2248,"222B,"007C,"2026,"2202,"00D7,"0302,
"2261,"0025,"22C5,"00B1,"2194,"21D4}]{Cambria Math}
```

The lines starting `\setmathfont` are what control the font for different characters. The option `\mathup` means the upright math style, while the `\mathit` option means the italic math style. The `/{num}` means to use the given font for all the numbers in the style given immediately prior and the `/{greek,Greek,latin,Latin}` means to use the given font for all the lower- and upper-case Greek and Latin letters in the given style. The last two lines are required because the `/{num}` option also includes a bunch of characters like square brackets `[`, the integral symbol, etc., but Times New Roman does not have definitions of these symbols. The following table shows the characters that did not print for me:

Unicode Character
2212 `−`
002B `+`
003D `=`
0028 `(`
0029 `)`
005B `[`
005D `]`
221A `√`
2211 `∑`
2248 `≈`
222B `∫`
007C `|`
2026 `…`
2202 `∂`
00D7 `×`
0302 `̂`
2261 `≡`
0025 `%`
22C5 `⋅`
00B1 `±`
2194 `↔`
21D4 `⇔`
2260 `≠`

These lines reset these characters to use the Cambria Math font. Now, all of my numerals are set in Times New Roman, no matter where they’re used.

Finally, note that `unicode-math` should be loaded after any other packages that mess with the math functionality, such as `amsmath` or `mathtools`.