Circle of Fifths Calculator

The circle of fifths arranges all twelve notes so each step around the circle is a fifth (7 semitones) apart, and that single relationship generates most of the key relationships musicians use every day. This calculator takes a Key Note and Mode and derives the Dominant Key (a fifth above the tonic, the harmonic center that pulls most strongly back to home), the Subdominant Key (a fourth above, or equivalently a fifth below), the Relative Key (the major/minor pair that shares the same key signature), the Parallel Key (same tonic note, opposite mode), and the number of Sharps (+) / Flats (-) in the key signature.

Key Note fully determines the Dominant and Subdominant Key results -- Mode has no bearing on either, since a fifth above C is G whether you're in C major or C minor. Key Note is also the dominant factor behind the Sharps (+) / Flats (-) result, since moving around the circle by key note changes the signature far more than switching between major and minor does; Mode still matters here because a minor key's signature matches its relative major, not the same note's major signature, so the calculator looks up the signature 3 semitones up from a minor tonic rather than directly at that note.