What Is an Interval
An interval is the distance from one note to another. Its number comes from the note letters it spans; its quality tells you the exact size in half steps. C to E and F to A are both thirds, even though they begin on different notes. Follow the interactive lesson below to learn more.
Measure a distance yourself
An interval is a distance you can count.
What you just learned
- Distance, not notes
Count the half steps
Count every key from one note to the next, black keys included. Seven half steps is a perfect fifth.
C → G = 7Read the full answer ↓ - Distance, not notes
Same distance, any start
Start on F and count seven again: another perfect fifth. The name follows the distance, not the notes.
F → C = 7Read the full answer ↓ - Count the half steps
One key flips the mood
Four half steps is a major third. One key lower, three half steps, is a minor third.
C E = 4 · C E♭ = 3Read the full answer ↓ - Number and quality
The number counts letters
C, D, E is three letters, so C to E and C to E flat are both thirds.
C D E = a thirdRead the full answer ↓ - All of them
Thirteen sizes in an octave
From 0 to 12 half steps, every distance has a name. Twelve brings you back to C, an octave up.
0 … 12 half stepsRead the full answer ↓ - Good to know
Flip it upside down
Move the bottom note up an octave and a third becomes a sixth. The two numbers always add up to nine.
3rd ↔ 6thRead the full answer ↓
Where to go from here
Every part of the lesson, answered in full
Open any question to read the full answer.
What does the number mean?
Count both the starting and ending letter. C-D-E contains three letter names, so every C-to-E interval is some kind of third. C-D-E-F-G contains five, so C to G is a fifth.
Sharps and flats do not change that number. C to E-flat is still a third because the endpoint is still a kind of E.
What does major, minor or perfect mean?
Quality gives the interval's exact size. C to E is four half steps and is called a major third. C to E-flat is three half steps and is called a minor third.
Unisons, fourths, fifths and octaves belong to the perfect family. Seconds, thirds, sixths and sevenths belong to the major-minor family. Any family can also produce augmented or diminished intervals when its normal size is expanded or contracted.
Keep number and quality separate
Number. Count letter names from the written starting note to the written ending note, including both ends.
Quality. Count the half steps and compare that size with the normal interval in its family.
Sound. Play the notes in sequence for a melodic interval or together for a harmonic interval. The name stays the same.
What are the intervals within one octave?
| Half steps | Common name | Example from C |
|---|---|---|
| 0 | perfect unison | C to C |
| 1 | minor second | C to D-flat |
| 2 | major second | C to D |
| 3 | minor third | C to E-flat |
| 4 | major third | C to E |
| 5 | perfect fourth | C to F |
| 6 | tritone | C to F-sharp or G-flat |
| 7 | perfect fifth | C to G |
| 8 | minor sixth | C to A-flat |
| 9 | major sixth | C to A |
| 10 | minor seventh | C to B-flat |
| 11 | major seventh | C to B |
| 12 | perfect octave | C to the next C |
Enharmonic spellings can name the same keyboard distance differently. C to F-sharp is an augmented fourth; C to G-flat is a diminished fifth. Both span six half steps, but their notation and harmonic meaning differ.
What happens when you invert an interval?
Move the lower note above the upper note and the interval inverts. The two numbers add to nine: a third becomes a sixth, a second becomes a seventh and a fourth becomes a fifth.
Major becomes minor, minor becomes major, augmented becomes diminished and perfect stays perfect. C up to E is a major third; E up to the next C is a minor sixth.
What is a compound interval?
An interval larger than an octave keeps the same basic quality while its number continues upward. A ninth is an octave plus a second, an eleventh is an octave plus a fourth and a thirteenth is an octave plus a sixth.
Chord symbols often use those compound names because register matters to voicing, even when the pitch class matches a simpler interval.
Name an interval without guessing
- 1. Ignore accidentals - count the letter names to get the number.
- 2. Count half steps - measure the exact keyboard distance.
- 3. Add the quality - major, minor, perfect, augmented or diminished.
- 4. Play it - hear it melodically and harmonically.
- 5. Move the root - rebuild the same interval from another note.