Guitar Chords in the Key of D Major

The chords in the key of D Major

D Major Chord D
E minor Chord Em
F minor Chord F♯m
G Major Chord G
A Flat Major Chord A
B Flat Minor Chord Bm
C Sharp Diminished Chord C♯dim

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

      D     Em    F#m   G     A     Bm    C#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)