Key Signature Calculator
Choose a tonic note and mode (major or minor) to see the key signature: how many sharps or flats it has and which ones.
What this calculator does
The Key Signature Calculator shows the key signature for any major or natural minor key: how many sharps or flats it has, and exactly which notes are affected throughout the piece.
How the calculation works
Key signatures follow the circle of fifths. Each step clockwise from C major adds one sharp, in the fixed order F#, C#, G#, D#, A#, E#, B#; each step counter-clockwise adds one flat, in the order Bb, Eb, Ab, Db, Gb, Cb, Fb. Every major key has a relative natural minor key that shares the exact same key signature, located three semitones below the major tonic (for example, C major and A minor both have no sharps or flats). The calculator looks up the correct number of accidentals for the chosen tonic and mode using this standard relationship.
This tool covers standard major and natural minor keys used in Western music notation. Harmonic and melodic minor scales add extra altered notes beyond the key signature itself, which are written in as needed rather than included in the signature.