What is a Perfect Eleventh?

A perfect eleventh is a musical interval that spans seventeen semitones. It can be understood as the distance of a perfect fourth extended by an octave. For example, the interval between C and F an octave higher is considered a perfect eleventh.

The sound of a perfect eleventh is similar to a perfect fourth but with a wider and more open quality because the notes are separated by an octave. This interval can create a spacious and powerful sound when used in harmony or chord structures. It often appears in extended chords where additional tones are added beyond the basic triad.

Perfect elevenths are commonly used in jazz, modern classical music, and contemporary harmony. For example, a C11 chord may include the notes C, E, G, B♭, D, and F, where the F above the octave forms the eleventh interval with the root. This interval adds richness and depth to musical arrangements and helps create fuller harmonic textures.