Perfect Intervals – What Makes Them So Perfect?

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So what exactly are perfect intervals?  What makes them so special to be called “perfect”? An interval is an interval, right?

Before we get into the deep logistics of perfect intervals, let’s go through a quick review of what an interval in music is first.

Fast Interval Review

In music theory, an interval is described as the distance between two notes.  Basically this is describing in greater detail how close or far apart two notes are from each other.

To define an interval, they are called unison, 2nd, 3rd, 4th, 5th, 6th, 7th or 8th (octave).


What is a Perfect Interval?

A perfect interval identifies the distance between the first note of a major scale and the unison, 4th, 5th or octave.   Only those intervals can be given the extra attached name as “perfect”.

perfect interval
perfect interval

PU/PP/P1 = Perfect Unison/Perfect Prime

P4 = Perfect Fourth

P5 = Perfect Fifth

P8 = Perfect Octave

In the example listed above, all of the perfect intervals are found within the C Major scale.

Why is it Called Perfect?

That is a very good question that involves more historical analysis into the times of antiquity in order to really answer it properly.  From my understanding, the term “perfect” originated due to the musical overtone series.

Apparently perfect intervals ring in a way that other intervals do not.  These sound qualities were first discovered and praised in the East.

A guy named Pythagoras was the first person from the West to explore this interesting observation.  He is responsible for incorporating it into our current musical language and practice.

The label of “perfect” in addition to a number describes the interval’s quality.  These intervals are called perfect because the ratios of their frequencies are simple whole numbers.

Another Tool to Use

If one of the interval notes does not include the first note of a scale, it can be a little trickier to find out what the quality of the interval is.  Just because the first note of any scale is not included does not mean it could not still be a perfect interval.

The way to find out is to count the number of half steps between the notes.

P1 = 0 half steps

P4 = 5 half steps

P5 = 7 half steps

P8 = 12 half steps

Start with the lower note and count in half steps moving up until you reach the last note.  This should help you decide if the interval truly is “perfect”.

Here are some examples of perfect intervals that do not include the first note of the C Major Scale as the bottom note even though they are all still found with the same scale:

perfect intervals

A perfect unison is very easy to find because both notes are exactly the same.  Likewise, a perfect octave is also simple to detect.  Both notes are the same except one of the notes are an octave (8 notes) higher or lower than the other note.

In Summary

1) Perfect intervals include adding a note above the first note of a major scale that represents the distance of a unison (prime), 4th, 5th or 8th (octave) interval.

2) A perfect interval does not have to include the first note of the major scale.  As long as both notes are found in the same major scale, they are considered diatonic intervals.  Using half steps as your guide will really help you determine what quality of intervals they are.

3) They are labeled as “perfect” because the sound quality is much different from any other intervals.

That is really all you need to know about perfect intervals!  The more you understand the language of music, the better you get at reading and playing!

Music Interval Practice Resources


    30 self-guided lessons and ready-to-use reproducible activity sheets for mastering intervals in music. They are ideal for choir, band, general music class, private lessons, and orchestra. Learn to recognize intervals through both sight and sound.

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    Learn music intervals in a fun and engaging way through these coloring pages. After identifying and coloring each interval, a unique geometric design appears.

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    Use these flash cards to practice learning and memorizing music intervals on the grand staff. It includes intervals of a 2nd through an octave. They are best for piano students.

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25 Replies to “Perfect Intervals – What Makes Them So Perfect?”


Thank you so much for such an informative little article. The question came up in our college band “What makes a perfect interval perfect?” You’re article was spot on, thanks!

So glad to hear this was helpful! Thanks for all the kind words and feedback 🙂

Wang Yandong

Hi Teresa, I love your website. This is really useful. Thank you!

Robyn Troncoso

Thank you for a concise explanation of the perfect interval in your article. The topic came up in a piano lesson with a student

Rowan Hill

I really like this website for the demystifying and easy to follow explanations.

I was intrigued by these ‘perfect’ intervals and, being a boring accountant, looked at the maths of the tone vibrations. The perfect octave of concert A (440Hz) rings at 880Hz – exactly two vibrations for every one vibration of the root tone. The perfect fourth rings at very close to 587Hz – one and one third vibrations for every one of the root tone. And the perfect fifth rings at very close to 660Hz – one and one half vibrations for every one of the root tone. I think when our ears hear these perfect intervals our brains neatly slot the faster vibrations in between the slower ones, tidily filling up the gaps, like completing a jigsaw. None of the other intervals have anywhere near such tidy ratios to the root tone, so they jar to some degree, like a jigsaw with missing (or extra) pieces.

Mathematically this all makes ‘perfect’ sense to me. Still battling with the piano though!

Thanks for this great musical resource.

Jon Forrest

You say “To define an interval, they are called unison, 2nd, 3rd, 4th, 5th, 6th, or 8th (octave).” but you show a staff that contains a 7th. What happened to the 7th in the sentence I quoted?

Thank you. I have made the correction.

Saffieuddin kashaf

U are simply genius the way u explained it was very different..i read about intervals but never without something not fully understood..this answered my questions perfectly..Thank you..

Thank you for the eloquent explanation, I had big headache understanding what P means,

Bookmarked! Thank you for this simple explanation. I couldn’t proceed forward without knowing WHY? Why is it perfect? Demystified it for me you did. 🙂

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