Perfect fourth interval
The perfect fourth interval consists of two notes separated by five semitones. For example, C to F note will result in this musical interval. The perfect fourth include one more semitone than a major third (M3) and two semitones fewer than a perfect fifth (P5).
The fourth and fifth are considered most consonant with perfect unison and perfect octave, and have been given the name perfect – the name goes back to the Medieval period. Perfect fourth is “perfect” in the sense that is almost sounds as the unison interval. The perfect fourth interval is abbreviated P4 (an alternate spelling is augmented third).
A perfect fourth with C to F on the keyboard.
Listen to the perfect fourth interval (C-F):
This interval is rare in chords, but can be found in the suspended 4th chord. For example, Csus4 is built by the notes C, F, G. If inversions are considered, they are much more common. For example, the second inversion of F major which is spelled C, F, A includes a perfect fourth.
To distinguish this interval by ear, a good idea is to think of familiar songs which first notes match. P4 examples are "House of the Rising Sun" (B-E) and "Moonlight Sonata" (G#-C#), in both cases ascending.
A perfect eleventh interval is an octave plus a perfect fourth (or compound perfect fourth, which is the correct term), which in total spans 17 semitones.
Ascending perfect fourth intervals
A list of ascending perfect fourth intervals:
- C – F
- C#/Db – F#/Gb
- D – G
- D#/Eb – G#/Ab
- E – A
- F – A#/Bb
- F#/Gb – B
- G – C
- G#/Ab – C#/Db
- A – D
- A#/Bb – D#/Eb
- B – E
Inversions of these intervals will result in perfect fifths.
Below is an example with ascending fourth intervals in pairs:
Descending perfect fourth intervals
A list of descending perfect fourth intervals:
- C#/Db – G#/Ab
- D – A
- D#/Eb – A#/Bb
- E – B
- F – C
- F#/Gb – C#/Db
- G – D
- G#/Ab – D#/Eb
- A – E
- A#/Bb – F
- B – F#/Gb
- C – G
Enharmonic notes such as Cb and Fb are omitted.
Below is an example with descending fourth intervals in pairs:
Augmented fourth (tritone)
A related interval is the augmented fourth, or tritone (abbreviated TT). It includes one additional semitone compared to the perfect fourth interval. For example, C to F#.
Listen to the perfect fourth interval (C-F#):
An augmented fourth C to F# on the keyboard.
Note that the augmented fourth is identical with the diminished fifth.
Read more about intervals and use the interactive Piano Interval Finder tool.