A simple guide to understanding key signatures

Last updated on May 25th, 2024


Key signatures are one of the essential music symbols to know when reading notation. In this guide we’ll explain what key signatures are, how to learn the symbols in all keys using the circle of 5ths and quick tips to find your music keys.

You’ll also be able to test your knowledge with a key signature quiz at the end of this lesson. Let’s get started.

What is a key signature?

A key signature is a symbol used in music notation to define the tonality of a piece of music and indicate the notes in a scale. Each key signature has a different amount of accidentals (sharp or flat notes) that define its scale. Instead of having to write a sharp or flat note every time it comes up, you can define this change throughout a piece of music using a key signature.

For example, here is a melody in the key of Db without a key signature.

sheet music without a key signature example

Now here is what the same notes in the previous example look like using a key signature.

sheet music using a key signature example

As you can see, using a key signature results in a much cleaner and more efficient way to notate music.

Chart of key signatures

Before showing you what all the keys signatures look like, it’s important to note that every Major key signature has a relative minor key signature that shares the exact notes except the starting points are different. For example, D Major and the relative B minor both share 2 sharps (F# and C#).

As you’ll see in the key signatures below, one sharp gets added after an interval of a 5th between the keys. Later on in the lesson, we’ll look at a chart of the circle of 5ths to help you visualize the changes between each key signature.

chart of key signatures in Major keys

Also, one flat gets added after an interval of a 4th between keys.

chart of key signatures in minor keys

Chart of key signatures with sharps

The exception below is C Major and it’s relative A minor which has no accidentals.

Major key signature Relative minor key signature Sharps
C MajorA minorNone
G MajorE minor1 sharp (F#)
D MajorB minor2 sharps (F#, C#)
A MajorF# minor3 sharps (F#, C#, G#)
E MajorC# minor4 sharps (F#, C#, G#, D#)
B MajorG# minor5 sharps (F#, C#, G#, D#, A#)
F# MajorD# minor6 sharps (F#, C#, G#, D#, A#, E#)

Chart of key signatures with flats

Major key signatureRelative minor key signatureFlats
F MajorD minor1 flat (Bb)
Bb MajorG minor2 flats (Bb, Eb)
Eb MajorC minor3 flats (Bb, Eb, Ab)
Ab MajorF minor4 flats (Bb, Eb, Ab, Db)
Db MajorBb minor5 flats (Bb, Eb, Ab, Db, Gb)
Gb MajorEb minor6 flats (Bb, Eb, Ab, Db, Gb, Cb)

Circle of 5ths

The circle of 5ths is often used in music theory to visualize the sharp and flatted notes in each key signature. It’s called the circle of 5ths because key signatures are separated by a distance of a 5th when moving in a clockwise direction.

For example, C to G is a distance of a 5th, G to D is a 5th, and so on. You’ll see that one sharp gets added as you move through each key signature in 5ths from C to F#.

The keys would change by 4ths if you count counterclockwise (C to F is a distance of a 4th interval, F to Bb is another 4th, and so on). One flat gets added as you move through each key signature in 4ths from C to Gb. You can see this in the chart below.

Circle of 5ths - chart


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How to quickly find a key signature

There are two methods for quickly finding key signatures depending on whether they are keys with sharps or flats. These tips will help you quickly know what key a song is in.

Tip to quickly find a key with sharps

Whenever you see sharps in a key signature, a quick way to find what key you are in is to count a half step up from the last sharp. For example, if the last sharp in a key signature is C#, count a half step up and you get the note D. You would be in the key of D Major or the relative B minor.

tip for finding sharp key signatures chart

If the last sharp in a key signature is D#, count a half step up and you are in the key of E.

tip for finding sharp key signatures chart 2

Tip to quickly find a key with flats

Whenever you see flats in a key signature, a quick way to find what key you are in is to look at the note in the second to last flat. The only exception for this is for the key of F which starts with one flat (Bb).

For example, if you have 3 flats in the key signature (Bb, Eb, Ab), count one before the last flat and you get the key of Eb Major.

tip for finding flat key signatures chart

Or if you have 5 flats in the key signature (Bb, Eb, Ab, Db, Gb), if you count one before the last flat and you get the key of Db Major.

tip for finding flat key signatures chart 2


Music Theory Quiz

Take this quiz to test your understanding of key signatures!


Major and minor scale formulas

Although learning key signatures are great for helping know the right notes of a scale, another way to think about scales is by using a formula for the distance between notes.

For example, every Major scale follows this same formula of whole steps and half steps: whole, whole, half, then whole, whole, whole, half.

Take a look at how to apply this formula to different Major scales below.

Major scale formula examples

And for minor scales, the formula for steps between each note is whole, half, whole, then whole, half, whole, whole.

See the formula application to minor scales below.

minor scale formula examples

Want to test your music theory skills? Take this quiz to find out.

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Wrapping up

In this lesson, we covered what key signatures are and how they are used in music notation. We also looked at how to use the circle of 5ths to understand how many accidentals each key contains.

It’s helpful to try memorizing each key signature so that you know the right notes to play scales or when composing music.

You may also want to check out the guide on time signatures to learn about another other essential music symbol.

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Best,

JG Music Lessons

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