lh
The height of one line of the element itself — rulers that match the text.
One lh is the computed line-height of the element itself: the exact height each line of text occupies there. Three lines measure 3lh, with no multiplying size by leading in your head.
It is the right choice for everything that must sit on the text's staff: a loading skeleton exactly two lines tall, a max-height: 5lh clamp that never beheads a line halfway, margins in line multiples to keep the vertical rhythm.
first line of the staff
second line of the staff
third line of the staff
.regua {
height: 3lh;
}