Major Key Signatures — Handy Guide Theory Things   William Wieland
Sharps:6
#
012345
 F  C  G  D  A  E  B 
Flats:10b
6
b
5
b
4
b
3
b
2
Explanation
Write the order of sharps. Eventually, this is all you will need.
        F  C  G  D  A  E  B 
C major has zero sharps. G has 1 sharp. D has 2, A 3, E 4, and B 5.
Sharps:012345
 F  C  G  D  A  E  B 
Continue counting on the other end. Add a # to the letter.

F sharp major has 6 sharps.
Sharps:6
#
012345
 F  C  G  D  A  E  B 
The order of flats is the order of sharps backwards. We number flats backwards.
C major has zero flats. F major has 1 flat, the first flat.
Sharps:6
#
012345
 F  C  G  D  A  E  B 
Flats:10
Continue counting on the other end. Add a b to each letter.
B flat major has 2 flats. E flat has 3, A flat 4, D flat 5, and G flat 6.
Sharps:6
#
012345
 F  C  G  D  A  E  B 
Flats:10b
6
b
5
b
4
b
3
b
2