However, you need to ensure you are always using the major scale of the note you're trying to work out.
You can use this rule for every other chord.
Take the C major scale, count the 1 note (C), then the 3 note and move it a semi-tone down (Eb), then the 5 note (G). Let's do a quick chord construction to understand this better… So, if we take the 3rd chord – it's a C minor chord, so you take the minor spelling (1, b3, 5) listed above, but use the C major scale, because the root note of the chord is C. To find the chords, you just plug the correct spelling into the root note major scale of what you're trying to find. We are going to show you exactly how to build each chord using chord spellings. For those of you that don't, don't worry. Those of you that know your chord shapes will be able to play the B flat major chord scale now.