Curious about the fonts available in the dropdown selector? Here’s the deal:
A few of them—Georgia, Times New Roman, Verdana, etc.—are system fonts commonly installed on Macs and PCs all over the world.
The remaining fonts are all Google Fonts, and they’re marked with a (G) in the dropdown selector.
Perhaps you noticed not all Google Fonts are available; this is because the Calculator only includes those with regular, bold, and italic faces—the minimum necessary to render text properly.
GRT Font Tuning
To generate the highest quality typographical recommendations, the Calculator fine-tunes all results based on the font you select.
This is especially critical when calculating line heights, as a minor correction is often needed to account for the physical characteristics of a particular font.
In this case, the most important characteristic is the x-height ratio; that is, the ratio of the height of a lowercase letter (x is the standard, hence the name) to the height of an uppercase letter (like a capital T).
The GRT Calculator applies a correction for fonts with an x-height ratio that is greater than or less than the golden ratio (φ).
Most fonts have an x-height ratio significantly greater than φ, and as a result, most recommended line heights end up being a little larger than what you’d get if you used the golden ratio alone.
In other words, fonts with a large x-height ratio need line heights that give them a little more “room to breathe.”