Key Signature
Find the key signature for any major or minor key, or identify a key from its sharps or flats. Free online music theory tool for musicians, composers, and students.
About This Calculator
The Key Signature Calculator is a free online music theory tool that helps musicians, composers, music students, and teachers quickly find key signatures or identify keys from sharps and flats. It works in two modes: finding the key from a given key signature (number of sharps or flats), or finding the key signature (which notes are sharped or flatted) from a given key name.
A key signature is a set of sharp or flat symbols placed at the beginning of each staff in sheet music that tells you which notes are consistently raised or lowered throughout a piece. There are 15 key signatures in standard Western music: 7 with sharps, 7 with flats, and C major/A minor with no sharps or flats. The calculator uses the circle of fifths to determine the correct accidentals for each key. For example, the key of D major has 2 sharps (F♯ and C♯), while the key of E♭ major has 3 flats (B♭, E♭, and A♭). Each major key has a relative minor that shares the same key signature, found by going down a minor third from the major root.
How key signatures work
To identify a key from its signature with sharps, look at the last sharp and go up one semitone — that is the major key. For example, if you see 3 sharps (F♯, C♯, G♯), the last sharp is G♯, so the key is A major. With flats, the second-to-last flat is the major key. For 4 flats (B♭, E♭, A♭, D♭), the penultimate flat is A♭, so the key is A♭ major. One flat (B♭) gives F major, and one sharp (F♯) gives G major — these are the two exceptions to the rule.
Regional notes
Key signatures are a universal concept in Western music notation used across all countries including India (in Western classical and jazz education), the United States, and the United Kingdom. The same 15 key signatures apply regardless of region. Mnemonics like 'Father Charles Goes Down And Ends Battle' (for sharps) and 'Battle Ends And Down Goes Charles Father' (for flats) are commonly taught in music schools worldwide including the Associated Board of the Royal Schools of Music (ABRSM) in the UK, state music programs in the US, and Western music conservatories in India.
Frequently Asked Questions
What is a key signature in music?
A key signature is a set of sharps or flats placed at the beginning of a staff in sheet music that indicates which notes are consistently sharped or flatted throughout a piece. It tells musicians what key the piece is in without requiring accidentals on every affected note.
How many key signatures are there?
There are 15 key signatures total: 7 with sharps, 7 with flats, and 1 with no sharps or flats (C major/A minor). Each corresponds to one major key and its relative minor key.
How do I find the key from a key signature?
For sharps: take the last sharp and go up a semitone (one half step) to find the major key. For flats: the second-to-last flat is the major key. For example, one sharp (F♯) gives G major, two flats (B♭, E♭) give B♭ major.
What is the order of sharps in a key signature?
The order of sharps is: F♯, C♯, G♯, D♯, A♯, E♯, B♯. A common mnemonic to remember this is 'Father Charles Goes Down And Ends Battle'.
What is the order of flats in a key signature?
The order of flats is: B♭, E♭, A♭, D♭, G♭, C♭, F♭. A common mnemonic to remember this is 'Battle Ends And Down Goes Charles Father' (reverse of the sharps mnemonic).
What key has no sharps or flats?
C major and its relative minor A minor have no sharps or flats. These are the only natural keys with no accidentals in their key signature.
What is the circle of fifths?
The circle of fifths is a visual diagram that shows the relationships between the 12 tones of the chromatic scale, their corresponding key signatures, and the relative minors. Moving clockwise adds sharps, moving counter-clockwise adds flats, and adjacent keys are a perfect fifth apart.
How do I find the relative minor of a major key?
To find the relative minor of a major key, count down three semitones (a minor third) from the major key's root note. For example, C major's relative minor is A minor, G major's relative minor is E minor, and D major's relative minor is B minor.