Interval Calculator
Pick two notes and get the interval's name, size in semitones and inversion — then press play and train your ear on it.
💡 the happy third — it makes major chords major
On guitar: 4 semitones = 4 frets up the same string.
Intervals are the atoms of music
An interval is just the distance between two notes, measured in semitones — one fret on the guitar, one key (black or white) on the piano. Chords are stacks of intervals, scales are sequences of them, and melodies are intervals walked one at a time. Get comfortable with the twelve of them and the rest of theory stops being memorization.
The two you should learn first
The major 3rd (4 semitones) and minor 3rd (3 semitones) are the emotional switch of music — they're the single note that makes a chord sound happy or sad. The perfect 5th (7 semitones) is the power-chord interval, so stable it's neither. Hear all three above, then spot them inside every chord in the chord finder.
Naming intervals is step one — hearing them blind is the skill. ThunderFret's adaptive ear-training quizzes play intervals and chords and target your weak spots.
Train your earFrequently asked
How do I work out the interval between two notes?
Count the semitones (half-steps) from the lower note up to the higher one. Each count has a name: 4 semitones is a major 3rd, 7 is a perfect 5th, 12 is an octave. On guitar, one fret = one semitone, so C to E is four frets = a major 3rd.
What is an interval inversion?
Flip which note is on top and the interval 'inverts': C up to E is a major 3rd, but E up to C is a minor 6th. Inversions always pair up to 12 semitones — knowing one gives you the other for free.
Why do intervals matter for guitar?
Every chord and scale is just a recipe of intervals — a major chord is a root, major 3rd and perfect 5th. Learn to see and hear intervals and you understand every shape you play instead of memorizing it.
What's the easiest way to learn interval sounds?
Anchor each one to a famous melody: a perfect 4th opens Here Comes the Bride, a perfect 5th opens the Star Wars theme, a minor 2nd is the Jaws motif. The calculator shows a hook like this for every interval, and ThunderFret's ear-training mode quizzes you on them.