Guitar Chords in the Key of B Flat (B♭) Major

The chords in the key of B♭ Major

B Flat Major Chord Bb
C minor Chord Cm
D minor Chord Dm
E Flat Major Chord Eb
F Major Chord F
G Minor Chord Gm
A Diminished Chord Adim

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

      Bb    Cm    Dm    Eb    F     Gm    Adim  
      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)