Article · Wikipedia archive · Last revised May 28, 2026

Augmented third

In classical music from Western culture, an augmented third is an interval of five semitones. It may be produced by widening a major third by a chromatic semitone. For instance, the interval from C to E is a major third, four semitones wide, and both the intervals from C♭ to E, and from C to E♯ are augmented thirds, spanning five semitones.

Last revised
May 28, 2026
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Wikipedia ↗
Augmented third
Inversediminished sixth
Name
Other names-
AbbreviationA31
Size
Semitones5
Interval class5
Just interval125:96,2 21:16, 64:49
Cents
12-Tone equal temperament500
24-Tone equal temperament500
Just intonation457

In classical music from Western culture, an augmented third (Playⓘ) is an interval of five semitones. It may be produced by widening a major third by a chromatic semitone.13 For instance, the interval from C to E is a major third, four semitones wide, and both the intervals from C♭ to E, and from C to E♯ are augmented thirds, spanning five semitones.

{ \override Score.TimeSignature #'stencil = ##f \relative c' { \time 4/4 \set Score.tempoHideNote = ##t \tempo 1 = 20 <ces e>1 <c? eis> } }

Being augmented, it is considered a dissonant interval.4

Its inversion is the diminished sixth, and its enharmonic equivalent is the perfect fourth.

The just augmented third, E♯, is 456.99 cents or 125:96. Playⓘ The Pythagorean augmented third, E♯+++, is 521.51 cents or 177147:131072, eleven just perfect fifths. Playⓘ

References

References

  1. Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.54. ISBN 978-0-07-294262-0.
  2. Haluska, Jan (2003). The Mathematical Theory of Tone Systems, p.xxvi. ISBN 0-8247-4714-3. Classic augmented third.
  3. Hoffmann, F.A. (1881). Music: Its Theory & Practice, p.89-90. Thurgate & Sons. Digitized Aug 16, 2007. Archaically: superfluous third.
  4. Benward & Saker (2003), p.92.