<P> The convention for the notation of key signatures follows the circle of fifths . Starting from C major (or equivalently A minor) which has no sharps or flats, successively raising the key by a fifth adds a sharp, going clockwise round the circle of fifths . The new sharp is placed on the new key's leading note (seventh degree) for major keys or supertonic (second degree) for minor keys . Thus G major (E minor) has one sharp which is on the F; then D major (B minor) has two sharps on F and C and so on . </P> <P> Similarly successively lowering the key by a fifth adds a flat, going counterclockwise around the circle of fifths . The new flat is placed on the subdominant (fourth degree) for major keys or submediant (sixth degree) for minor keys . Thus F major (D minor) has one flat which is on the B; then B ♭ major (G minor) has two flats (on B and E) and so on . </P> <P> Put another way: for key signatures with sharps, the first sharp is placed on F with subsequent sharps on C, G, D, A, E and B; for key signatures with flats, the first flat is placed on B with subsequent flats on E, A, D, G, C and F. There are thus 15 conventional key signatures, with up to seven sharps or flats and including the empty signature of C major (A minor). </P> <Ul> <Li> Starting from a key with flats in its key signature: raising by fifths successively reduces the flats to zero at C major (A minor). Further such raising adds sharps as described above . </Li> <Li> Starting from a key with sharps: lowering by fifths successively reduces those sharps to zero . Further such lowering adds flats as described above . </Li> <Li> When the process of raising by a fifth (adding a sharp) produces more than five or six sharps, successive such raising generally involves changing to the enharmonic equivalent key using a flat - based signature . Typically this is at F ♯ = G ♭, but may also be at C ♯ = D ♭ or B = C ♭ . The same principle applies to the process of successive lowering by a fifth . </Li> </Ul>

The order of sharps in a key signature is