What Is an Interval in Music?
A musical interval is the distance between two notes, which we can also describe as the difference in pitch between two sounds. In physical terms, it is the ratio between the vibrational frequencies of notes.
Notes in music theory are sounds with determined frequencies. English-speaking countries named the sounds in the C major scale (the white keys on a piano) with the first seven letters of the Latin alphabet: C, D, E, F, G, A, B. Another standard system for naming these sounds is solfège, which uses the syllables: Do, Re, Mi, Fa, Sol, La, Si.
Intervals may be counted in semitones. A semitone is the smallest unit of a musical distance commonly used in Western music. It is the distance between any two notes on adjacent keys (on a piano) or frets (on a guitar).
What Is an Octave?
An octave is the interval spanning 8 diatonic notes (12 semitones). When a note doubles its frequency, it sounds "the same" but higher — and this relationship is called an octave. On a standard piano, there are 8 full octaves (C0 through C8). In scientific pitch notation, octave numbers identify which register a note belongs to (e.g., A4 = 440 Hz, the standard concert pitch).
Accidentals in Music
Accidentals are symbols that raise or lower the pitch of a note:
- ♯ (sharp) — raises the note by one semitone (e.g., F♯ is one semitone above F)
- ♭ (flat) — lowers the note by one semitone (e.g., B♭ is one semitone below B)
- ♮ (natural) — cancels a previous accidental, restoring the note to its original pitch
- ♯♯ (double sharp) — raises the note by two semitones
- ♭♭ (double flat) — lowers the note by two semitones
Enharmonic equivalents are notes that sound the same but are written differently, such as C♯ and D♭ (both are 1 semitone above C). When you use the "By Note Names" mode, the calculator differentiates between enharmonic equivalents and gives you the interval quality for each specific spelling.
Musical Intervals Chart
| Symbol | Name | Semitones | Example |
|---|---|---|---|
| P1 | Perfect Unison | 0 | C → C |
| m2 | Minor Second | 1 | C → D♭ |
| M2 | Major Second | 2 | C → D |
| m3 | Minor Third | 3 | C → E♭ |
| M3 | Major Third | 4 | C → E |
| P4 | Perfect Fourth | 5 | C → F |
| A4 / d5 | Augmented Fourth / Diminished Fifth (Tritone) | 6 | C → F♯ / C → G♭ |
| P5 | Perfect Fifth | 7 | C → G |
| m6 | Minor Sixth | 8 | C → A♭ |
| M6 | Major Sixth | 9 | C → A |
| m7 | Minor Seventh | 10 | C → B♭ |
| M7 | Major Seventh | 11 | C → B |
| P8 | Perfect Octave | 12 | C4 → C5 |
| M9 | Major Ninth (compound) | 14 | C4 → D5 |
How to Use the Music Interval Calculator
The calculator has two modes:
- By Pitches (with Octave) — Select both the note name and octave for each pitch. This gives you the exact interval including direction (ascending or descending) and handles compound intervals (intervals larger than an octave, like a 9th or 11th).
- By Note Names — Select just the note name and accidental, without specifying octaves. The calculator shows both the ascending and descending intervals within one octave.
Determine an Interval Between Two Pitches
To find the interval between two specific pitches (e.g., A4 and C5):
- Select "By Pitches (with Octave)" mode
- Set the first note: A, natural (♮), octave 4
- Set the second note: C, natural (♮), octave 5
- Click "Find Interval"
- Result: Minor Third (3 semitones, ascending)
Determine an Interval Between Two Notes
To find the quality of an interval between note names (e.g., F and C):
- Select "By Note Names" mode
- Set the first note: F, natural (♮)
- Set the second note: C, natural (♮)
- Click "Find Interval"
- Result: Perfect Fifth ascending (7 semitones), Perfect Fourth descending (5 semitones)
How to Get from F to C — Example
The interval from F up to C is a Perfect Fifth (spanning 5 diatonic steps: F–G–A–B–C, or 7 semitones).
The interval from C up to F is a Perfect Fourth (spanning 4 diatonic steps: C–D–E–F, or 5 semitones).
These two intervals are inversions of each other: a Perfect Fifth inverts to a Perfect Fourth, and vice versa. The sum of their semitones is always 12 (one octave).
Interval Quality Explained
Intervals are classified by both their number (how many diatonic scale steps apart) and quality:
- Perfect — applies to unisons, fourths, fifths, and octaves. These have a very stable, consonant sound.
- Major — applies to seconds, thirds, sixths, and sevenths at their larger size.
- Minor — applies to seconds, thirds, sixths, and sevenths at their smaller size (one semitone less than major).
- Augmented — one semitone larger than a perfect or major interval.
- Diminished — one semitone smaller than a perfect or minor interval.
- Doubly Augmented / Doubly Diminished — two semitones away from perfect/major.
Simple vs. Compound Intervals
A simple interval spans at most one octave (up to 12 semitones). A compound interval is larger than an octave and can be reduced to its simple equivalent:
- A 9th = 2nd + 1 octave (e.g., Major 9th = Major 2nd + octave)
- A 10th = 3rd + 1 octave (e.g., Minor 10th = Minor 3rd + octave)
- An 11th = 4th + 1 octave, and so on.
FAQs
What is the smallest musical interval?
The semitone (also called a half step or minor second) is the smallest interval in standard Western music. It is the distance between adjacent keys on a piano keyboard.
What is a tritone?
A tritone is the interval of exactly 6 semitones — exactly half an octave. It can be spelled as an Augmented Fourth (e.g., C to F♯) or a Diminished Fifth (e.g., C to G♭). These are enharmonic equivalents but are written differently depending on the musical context.
Why are some intervals called "perfect"?
Unisons, fourths, fifths, and octaves are called "perfect" because they have a very pure acoustic quality and appear naturally in the harmonic series. They were considered the most consonant intervals in early Western music theory.
What is the difference between C♯ and D♭?
They sound the same on a modern keyboard (both are 1 semitone above C and 1 semitone below D). However, they are spelled differently and represent different intervals in music theory. C♯ forms an Augmented Second above B, while D♭ forms a Minor Second above C. The "By Note Names" mode in our calculator handles this distinction.