The Family of G Chords
G = G - B - D
Gmaj7 = G - B - D - F#
G7 = G - B - D - F
Gm7 = G - Bb - D - F
Gm7(b5) or Gø7 = G - Bb - Db - F
Gdim7 = G - Bb - Db - Fb
Gdim = G - Bb - Db
It's easier to think of a diminished chord as a minor chord with a flatted 5th. Gm = G - Bb - D
So then, what's the formula for a minor chord?
Just look a the first chord at the top of this list, the G major chord, and lower the middle note a half step. Congratulations! You've come full circle.