Guitar Chord Numbering

one, four, five in every key

To organize chords, we can utilize a guitar chord numbering system. We name a particular chord, the one chord (also known as the tonic). Once a chord is named the one (I), it's alphabetical from there. So, if A is the one chord, D is the four chord (IV), & E is the five chord (V). If A is 1, D is 4, & E is 5.

One way guitar chords can be built - EON

Guitar chord numbering is a great way to keep track of relationships between chords. It is important to memorize (move information to pure knowledge) the relationships between chords.

Practice playing the blues progressions by substituting these triads in those progressions. And, take a look at this set.

And, definitely memorize the relationships, starting with C, G, D, A, & E (the main 'guitar keys'). This knowledge plus a capo gets us functional in all keys.


  • The I chord is called the Tonic.
  • The ii chord is called the Super Tonic.
  • The iii chord is called the Mediant.
  • The IV chord is called the Subdominant - called this because it is the dominant below the tonic (5 tones below the I chord), not because it is one under the Dominant.
  • The V chord is called the Dominant.
  • The vi chord is called the Submediant. The Mediant is 3 chords above the tonic, the Submediant is 3 chords below. Similar to the Dominant naming scheme.
  • The viio chord is called the Leading Tone chord.

Progressive Harmony

Tonics like to move to Subdominants. Subdominants like to move to Dominants. Dominants like to go to Tonics. When chords follow this progression ( I to IV to V to I), this is considered progressive harmony (regressive being the reverse).

guitar harmony

triads in all keys, chord numbering

We left off the viio chord because we rarely use them. The tones of the diminished chord are the 3rd, 5th, and 7th of the Dominant 7 chord. We can use the V7 chord in place of the viio.