An interval is the distance between two musical notes. Every chord, scale, and melody is built from intervals — understanding them unlocks the entire language of music theory.
An interval is simply the distance between two notes. On the piano, you can count that distance by counting the keys between them — including black keys. Each key-to-key step is one half-step (also called a semitone).
The five most important intervals to know first: the unsettling minor 2nd, the "happy" major 3rd, the powerful perfect 5th, the fusing octave, and the notorious tritone. Press each button below to hear and see them.
These four concepts build on each other. A note is a single pitch. An interval is the distance between two notes. A chord is three or more notes sounding together (stacked intervals). A scale is a sequence of notes ordered by their intervals from a root.
Click each tile below to hear the difference and see which keys are involved.
The half-step (semitone) is the smallest interval on the piano — the distance between any key and its immediate neighbour, black or white. E to F is a half-step. B to C is a half-step. C to C♯ is a half-step.
A whole-step (tone) is exactly two half-steps — one key in between. C to D is a whole-step (C♯ in the middle). E to F♯ is a whole-step (F in the middle).
Click any two keys on the keyboard below to measure the distance between them. The widget will count the half-steps and name the interval.
Every interval has two components in its name: a number and a quality. Together they give you the full name: “Major 3rd,” “Perfect 5th,” “Minor 7th.”
Count the letter names spanned, including both endpoints. C to E spans C, D, E — that's three letter names, so it's a 3rd. C to G spans C, D, E, F, G — five letter names, so it's a 5th. This is always the first step, and it never changes even when notes are sharp or flat.
The quality tells you the exact size within that number. There are five qualities:
The four perfect intervals — unison, perfect 4th, perfect 5th, and octave — get their name from their uniquely pure frequency ratios. The octave is 2:1 (double the frequency). The perfect 5th is 3:2. The perfect 4th is 4:3. These ratios are so clean that the notes seem to fuse rather than clash.
Perfect intervals are neither major nor minor — they sit in their own quality category. And unlike major/minor intervals, they have no “parallel” version on the other side: there is no “major 5th” or “minor 4th” in standard nomenclature.
Select a root note below, then click each perfect interval tile to hear it from that root.
The 2nd, 3rd, 6th, and 7th each come in two flavors: major (larger, brighter, more open) and minor (one half-step smaller, darker, more inward). Major intervals appear in major scales; minor intervals appear in minor scales — which is where the names come from.
The difference is always exactly one half-step. A major 3rd is 4 half-steps; a minor 3rd is 3. A major 6th is 9 half-steps; a minor 6th is 8. This single half-step shift produces the emotional contrast between “happy” and “sad” that defines so much of Western music.
Select a root, then toggle between the A (major) and B (minor) version of each interval pair.
When you expand a perfect or major interval by one half-step, it becomes augmented. When you shrink a perfect or minor interval by one half-step, it becomes diminished. These are the outermost edges of the quality spectrum.
The most important augmented/diminished interval is the tritone — 6 half-steps, exactly half an octave. It has a unique identity: it can be called either an augmented 4th (C to F♯) or a diminished 5th (C to G♭). Both are 6 half-steps — the same piano keys, different spellings.
Medieval music theorists called it the diabolus in musica (devil in music) and avoided it. Jazz and blues composers embraced it as the ultimate tension interval.
Consonance describes intervals that sound stable, restful, and resolved on their own. Dissonance describes intervals that feel tense, unsettled, and like they want to move. The distinction is not absolute — it's a spectrum, and context matters enormously.
The traditional classification:
The fastest path to recognizing intervals by ear is melodic association: link each interval to the opening notes of a memorable song. Once you've heard “Perfect 5th = Star Wars” enough times, you'll hear that leap in any context — even when it's not from C.
Press Play Interval to hear a random interval played sequentially then harmonically. Try to identify it before clicking an answer.
To invert an interval, flip which note is on top. If you have C below E (a major 3rd going up), invert it by putting E on the bottom and C on top — now it's a minor 6th going up.
Two elegant rules govern inversions:
Select an interval below, then press Invert to see and hear what it becomes.
A compound interval spans more than an octave. They're named by adding an octave to the simple version: a 9th is a 2nd plus an octave, a 10th is a 3rd plus an octave, an 11th is a 4th plus an octave, and so on.
The quality follows the same pattern as the simple interval. A major 9th is just a major 2nd stretched by an octave — same brightness, just more expansive. This is why jazz musicians talk about “9th chords” — they're adding the major 2nd an octave above.
All 13 intervals from unison to octave, with their abbreviation, half-step count, frequency ratio, consonance classification, and a melodic mnemonic for ear training.
| Name | Short | Half-Steps | Ratio | Class | Sound Character | Mnemonic |
|---|---|---|---|---|---|---|
| Perfect Unison | P1 | 0 | 1:1 | ✓ Consonant | Same pitch | Same note |
| Minor 2nd | m2 | 1 | 16:15 | ✗ Dissonant | Tense, dissonant | "Jaws" theme |
| Major 2nd | M2 | 2 | 9:8 | ✗ Dissonant | Stepwise, neutral | "Happy Birthday" |
| Minor 3rd | m3 | 3 | 6:5 | ✓ Consonant | Sad, warm | "Smoke on the Water" |
| Major 3rd | M3 | 4 | 5:4 | ✓ Consonant | Happy, bright | "When the Saints" |
| Perfect 4th | P4 | 5 | 4:3 | ✓ Consonant | Open, stable | "Here Comes the Bride" |
| Tritone | TT | 6 | √2:1 | ✗ Dissonant | Unstable, ominous | "The Simpsons" |
| Perfect 5th | P5 | 7 | 3:2 | ✓ Consonant | Strong, open | "Star Wars" |
| Minor 6th | m6 | 8 | 8:5 | ✓ Consonant | Bittersweet | "The Entertainer" (inv) |
| Major 6th | M6 | 9 | 5:3 | ✓ Consonant | Warm, nostalgic | "My Way" |
| Minor 7th | m7 | 10 | 16:9 | ✗ Dissonant | Tense, bluesy | "Somewhere" (bridge) |
| Major 7th | M7 | 11 | 15:8 | ✗ Dissonant | Dreamy, yearning | "Take On Me" |
| Perfect Octave | P8 | 12 | 2:1 | ✓ Consonant | Pure, complete | "Somewhere Over the Rainbow" |
Intervals are the atoms of music theory. Once you understand them, everything else becomes derivable rather than memorizable:
The time you invest in drilling intervals pays compound returns across every other area of music theory and performance. It's the highest-leverage skill in musicianship.
Every chord, scale, and melody you hear is a web of intervals. With this foundation in place, you can decode the harmonic language of any song — and build your own.