Guitar Chords in the Key of A Major

The chords in the key of A Major

A Major Chord A
B flat minor Chord Bm
C Sharp minor Chord C♯m
D Major Chord D
E Major Chord E
F Sharp minor Chord F♯m
G Sharp diminished Chord G♯dim

A Major - B minor - C♯ minor - D Major - E Major - F♯ minor - G♯ diminished (G♯°).

      A     Bm    C#m   D     E     F#m   G#dim 
      I     ii    iii   IV    V     vi    vii   

The chord formula for any Major key is
Major - minor - minor - Major - Major - minor - diminished

A common way to number these chords is by Roman numerals
I - ii - iii - IV - V - vi - vii

(Major chords are usually capitalized, minor and diminished chords are lower case)