Circle of fifths and key signature finder.

How does the circle of fifths show key signatures?

Moving clockwise round the circle of fifths from C, each key is a perfect fifth higher and adds one sharp: G has one, D has two, A three and so on. Moving anticlockwise, each key is a fifth lower and adds one flat: F has one, B♭ two, E♭ three. Sharps are added in the order F♯ C♯ G♯ D♯ A♯ E♯ B♯ and flats in the order B♭ E♭ A♭ D♭ G♭ C♭ F♭. A major key and its relative minor share a key signature; the relative minor starts on the sixth degree of the major scale, three semitones below the tonic.

Worked examples. D major has two sharps (F♯, C♯), its relative minor is B minor, the key up a fifth is A major and the key down a fifth is G major. E♭ major has three flats (B♭, E♭, A♭) and its relative minor is C minor. In a major key the triads are I, ii, iii, IV, V, vi and vii°; in natural minor they are i, ii°, III, iv, v, VI and VII. Keys needing more than seven sharps or flats, such as G♯ major, are not listed; their enharmonic keys are used instead.