Pick one base size and one ratio, and every other text size on the page falls out of the multiplication. Here is the whole scale on a real article, the exact numbers, and the CSS to paste.
Puts a second scale next to this one, same copy, same base — so you can see which ratio actually reads better.
A modular scale is one number multiplied over and over. Body text is the base. One step up is
base × ratio, two steps up is base × ratio², and a step down divides instead.
Small ratios like 1.125 give you a quiet, dense page where headings barely lift off the text; big ones like
1.618 give you a page that shouts at the top and whispers at the bottom. Nothing in between gets invented,
which is the whole point — the sizes relate to each other instead of being picked one at a time.
Line height here is not one number. It starts at your body value and shrinks as text gets bigger, by the
tighten amount per doubling of size, because a 48px headline set at 1.55 looks like it is falling apart.
The rem column assumes the browser default root of 16px, so 1rem is 16px even when your base is 19px.
Rounding to whole pixels is on by default because that is what browsers do to your text anyway; turn it off and
watch the fractional values appear. If two neighbouring steps round to the same pixel, the panel says so —
that is a real scale that has run out of room at the small end.