Typography can make or break a designTypography can make or break a design

When a layout feels cheap and nobody can say why, the cause is almost always typographic. Not the choice of face — the ordering. Too many sizes, too many weights, and nothing that tells the eye where to go first.

It helps to separate two things that get used interchangeably. Legibility is whether you can distinguish one letter from another, which is a property of the typeface and its size. Readability is whether someone can comfortably get through a paragraph, which is mostly a property of what you did with it: line length, line spacing, tracking, alignment. A very legible typeface set badly is still unreadable.

Hierarchy is the part that carries a design. It is built from a small number of deliberate steps — a scale — rather than from picking sizes by eye. Working from a ratio means the relationships stay consistent across a whole system, and it removes the argument about whether a subhead should be 19 or 20 points.

Spacing does more than size does. Line height in the region of 1.2 to 1.5 times the type size is the usual working range, tighter for large display and looser for long text. Line length matters as much: too long and the eye loses its place returning to the left margin.

The discipline I would give anyone starting out is to use fewer sizes than feels comfortable. Three is usually enough. If a layout needs a fourth, the problem is often that the content has not been organised, and no amount of typographic variety will fix a structure that has not been decided.