Common guitar chord progressions

A chord progression is the order of chords in a song. A handful of progressions turn up again and again; learn them once and you can play them in any key.

Questions

What do the Roman numerals mean?

Each numeral is a step of the key's scale: I is the home chord, IV and V are built on the fourth and fifth notes. Uppercase means a major chord, lowercase a minor chord.

What is the most common chord progression?

I–IV–V is the oldest and most widespread, and I–V–vi–IV is the most common in modern pop.

Which progressions sound sad?

Progressions that start on a minor chord, such as vi–IV–I–V or the minor i–VI–III–VII, have a darker, more emotional sound.