SEMITONES

A semitone is the distance from 1 key/fret to the next...

FRETS>>>> 1st 2nd  3rd 4th  5th 6th  7th 8th 9th 10th 11th 12th

E-string - F - F# - G - G# - A - A# - B - C - C# - D - D# - E
B-string - C - C# - D - D# - E - F - F# - G - G# - A - A# - B
G-string - G# - A - A# - B - C - C# - D - D# - E - F - F# - G
D-string - D# - E - F - F# - G - G# - A - A# - B - C - C# - D
A-string - A# - B - C - C# - D - D# - E - F - F# - G - G# - A
E-string - F - F# - G - G# - A - A# - B - C - C# - D - D# - E

FRETS>>>> 1st 2nd  3rd 4th  5th 6th  7th 8th 9th 10th 11th 12th

E-string - F - Gb - G - Ab - A - Bb - B - C - Db - D - Eb - E
B-string - C - Db - D - Eb - E - F - Gb - G - Ab - A - Bb - B
G-string - Ab - A - Bb - B - C - Db - D - Eb - E - F - Gb - G
D-string - Eb - E - F - Gb - G - Ab - A - Bb - B - C - Db - D
A-string - Bb - B - C - Db - D - Eb - E - F - Gb - G - Ab - A
E-string - F - Gb - G - Ab - A - Bb - B - C - Db - D - Eb - E

Now tell me...

How many semitones from C to C#? - - - 1 semitone

How many semitones from C to D? - - - 2 semitones

How many semitones from D to G? - - -  5 semitones

How many semitones from G to G#? - - - 1 semitone

How many semitones from G# to B? - - - 3 semitones

How many semitones from Eb to A? - - - 6 semitones

How many semitones from F# to Ab? - - - 2 semitones

How many semitones from F# to Bb? - - - 4 semitones

How many semitones from C to the next C? - - - 12 semitones

Ok, now:

How many semitones from G to Gb? - - - it can be either 11 or 1 depending on which direction we're counting...so if we're counting up the keyboard (or fretboard), then there would be 11 semitones from G to Gb

...but if we're counting down, then there would only be 1 semitone between G and Gb!

So let's rework the above examples...

How many semitones from C to C#? - - - either 1 semitone or 11 semitones

How many semitones from C to D? - - - either 2 semitones or 10 semitones

How many semitones from D to G? - - -  either 5 semitones or 7 semitones

How many semitones from G to G#? - - - either 1 semitone or 11 semitones

How many semitones from G# to B? - - - either 3 semitones or 9 semitones

How many semitones from Eb to A? - - - either 6 semitones or 6 semitones

How many semitones from F# to Ab? - - - either 2 semitones or 10 semitones

How many semitones from F# to Bb? - - - either 4 semitones or 8 semitones

How many semitones from C to C? - - - either 12 semitones or 0 semitones

...as you can tell, if you add up those numbers above they will always add up to 12...

1+11=12

2+10=12

5+7=12

...etc...