Guitar Chords in the Key of C Major

The chord formula for any Major key is Major, minor, minor, Major, Major, minor, diminished.

The chords in the key of C major are C Major, D minor, E minor, F Major, G Major, A minor, and B diminished.

A common way to number these chords is by Roman numerals: I, ii, iii, IV, V, vi, vii. Numerals that represent a major chord are usually capitalized, and minor and diminished chords are lower case.