---
title: "Musical Intervals: How to Count and Name Them · Piakno"
description: "An interval is the distance between two notes, counted including both ends: C up to E passes C, D, E, so it is a third. The number says how far; the word in front — major, minor, perfect — says which kind."
url: "https://piakno.com/theory/intervals"
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# Intervals

> An interval is the distance between two notes, counted including both ends: C up to E passes C, D, E, so it is a third. The number says how far; the word in front — major, minor, perfect — says which kind.

Always count both ends. C to D is a second, not a first, and C to C is a unison. That runs against the instinct to count the gaps rather than the letters, and it is the first place beginners get stuck.

*C up to E: three letters, C D E, so a third — and four half steps, so a major third.*

*C up to G: five letters, so a perfect fifth.*

The number alone is not enough, because two thirds can differ by a half step: C–E spans four half steps (major third), C–E♭ spans three (minor third). So each number takes a quality word. Seconds, thirds, sixths and sevenths come in major and minor; unisons, fourths, fifths and octaves are called perfect, because they have no major or minor form.

| Interval | Half steps | From C |
| --- | --- | --- |
| Minor 2nd | 1 | C–D♭ |
| Major 2nd | 2 | C–D |
| Minor 3rd | 3 | C–E♭ |
| Major 3rd | 4 | C–E |
| Perfect 4th | 5 | C–F |
| Perfect 5th | 7 | C–G |
| Major 6th | 9 | C–A |
| Perfect octave | 12 | C–C |

> On the staff you can read the number off the geometry: line to line, or space to space, is always an odd number (third, fifth); line to space is always even (second, fourth). That is much faster than counting letters one at a time.

## How do you invert an interval?

To invert an interval, move its lower note up an octave (or its upper note down one). The two numbers always add up to 9, so a third becomes a sixth, a second a seventh and a fourth a fifth. The quality flips: major becomes minor, minor becomes major, augmented becomes diminished and diminished becomes augmented. Perfect stays perfect.

*E up to C: a minor sixth, the major third C–E turned upside down.*

| Interval | Inverts to | Example |
| --- | --- | --- |
| Major 2nd | Minor 7th | C–D → D–C |
| Minor 3rd | Major 6th | C–E♭ → E♭–C |
| Major 3rd | Minor 6th | C–E → E–C |
| Perfect 4th | Perfect 5th | C–F → F–C |
| Augmented 4th | Diminished 5th | C–F♯ → F♯–C |

## What is a compound interval?

An interval wider than an octave is a compound interval. It is named by counting on: a ninth is an octave plus a second, a tenth an octave plus a third, and so on. To find its quality, subtract 7 from the number and read the simple interval left over, so C up to the E in the next octave is a major tenth, an octave plus a major third. Chord symbols use these names for their extensions: the 9 in Cmaj9 is the D above the octave.

> Both rules are about numbers, not about the keyboard, so counting letters still works. From C up to the D in the next octave is C D E F G A B C D, nine letters, so a ninth.

## Common questions

### What is an interval in music?

The distance between two notes, named by how many letter names it spans. C to G spans five of them, so it is a fifth.

### How do you count an interval?

Count the starting note as 1 and every letter name up to the top note, ignoring sharps and flats. D up to A is D E F G A, so a fifth; the accidentals only decide the quality.

### What is the difference between a major and a minor third?

A major third is four half steps (C–E) and a minor third is three (C–E♭). The major third gives a brighter color and the minor a darker one, and that single half step separates major triads from minor ones.

### How do you invert an interval?

Lift the bottom note an octave. The new interval is the one that completes the octave: a minor third turns into a major sixth, and a perfect fifth into a perfect fourth.

## The course works through this in:

- [Lesson 52 · Seconds and thirds](https://piakno.com/course/piano-foundations/lesson/52)

## Related entries

- [Whole steps and half steps](https://piakno.com/theory/whole-and-half-steps)
- [Major and minor triads](https://piakno.com/theory/major-and-minor-triads)
- [The circle of fifths](https://piakno.com/theory/circle-of-fifths)

- [Theory reference](https://piakno.com/theory)