Key Signature Calculator

Find the key signature, accidentals, and relative key for a major or minor tonic.

918.3K uses Updated · 2026-05-21 Runs locally · zero upload
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How to Use Key Signature Calculator

Enter a tonic such as C, F#, Bb, or Eb, then choose major or minor. The calculator returns the key name, number of sharps or flats, the accidental names in order, and the relative major or minor key. Use flats in the input when you prefer flat spelling, and sharps when you prefer sharp spelling.

Formula & Theory - Key Signature Calculator

Major key signatures follow the circle of fifths. For minor keys, the calculator first finds the relative major by moving up three semitones from the minor tonic, then uses that major key signature. Accidentals are listed using the standard sharp order F#, C#, G#, D#, A#, E#, B# or flat order Bb, Eb, Ab, Db, Gb, Cb, Fb.

relativeMajorIndex = minorTonicIndex + 3 semitones
keySignature = circleOfFifthsLookup(relativeMajor or majorTonic)

Use Cases for Key Signature Calculator

Use it for composing, arranging, sight-reading prep, music theory homework, choosing a notation spelling, or quickly checking how many sharps or flats belong to a key before writing a score.

Frequently asked questions about Key Signature Calculator

How do I use Key Signature Calculator?

Enter the tonic and choose major or minor. The calculator returns accidentals, accidental count, and the relative key.

What formula or rule does Key Signature Calculator use?

It looks up major signatures by circle-of-fifths data; minor keys are converted to their relative major by moving up three semitones.

Is my data stored?

No. All calculations happen in your browser; nothing is sent to a server.