Actually the title of this article is a bit deceiving. We actually do not have a width of the fretboard at the saddle. What we do have though is the width of the fretboard at the soundhole is definitely influenced by the saddle width. Now that makes more sense. With electric guitars, it would be the width of the fretboard at the fretboard pickup.
What Determines The Saddle Width:
Much like the discussion on nut width, variations in the saddle are driven by the type of music or style of playing the guitar player will be engaged in for the majority of their time.
Usually fingerstyle guitar players like a slightly wider string spread at the saddle than do flatpick guitar players or electric guitar players. This spacing can also be influenced by the size of an individuals fingers or the length of the fingers, so it really boils down to guitar player preferences.
Fingerstyle guitarists usually prefer to have a string spread a bit closer to a classical guitar. A standard flatpick acoustic guitar will have about 53 to 54 mm at the saddle. A standard concert classical will have about 60 mm and a fingerstyle acoustic will be somewhere in-between at around 57 to 58 mm.
12 String Acoustic Guitars:
With the introduction of the 12 string acoustic guitar, it was determined that keeping the fretboard at standard 6-string spacing did not allow enough room for those extra 6 strings, so the fretboard at the nut was widened out about 1/8″ or so, to keep the center to center spacing of the strings at a comfortable spacing. This amounted to about 2-5/16″ or about 58 mm, which is about the same as the fingerstyle acoustic.
I fall into this category, so don’t take the name as an insult. I would be termed a crossbreed because I started playing on an electric guitar, moved on to a concert classical and ended up with a steel string acoustical. Now how do you make a guy like me happy with fretboard width? You actually stretch the acoustic dimension a bit and shrink the classical a bit and meet somewhere in the middle. So I am happiest playing an Acoustic Guitar with a fretboard saddle width of about 2-3/16″ to 2-1/4″ or right around 56 mm. Classical Guitar fretboards at standard width are of course perfectly fine with me, but would be too wide for most guitar players.
Usually, you will find that the out-to-out dimension of the fretboard (including any binding etc.) will be about the same dimension at the 12th fret as the string spacing is at the saddle. This is not a rule that is set in stone, but it sure is a good starting point.
String Inset Dimensions:
The string inset dimension was discussed at the nut end of things, we should now talk about the inset of the strings at the 12th fret, which is the standard point we measure this dimension.
Usually because the strings gain elevation as you progress down the fretboard, they are not only at nearly a high point at the 12th fret, but they are their loosest at the point because it is the midpoint of the scale length and thus the middle of the string.
If we kept the string inset from the edge of the fretboard the same dimension as it is at the nut of the guitar, you would find that the string would pull off the edge of the fretboard without much effort. Therefore, we need to add some additional space between the fretboard edge and the center of the outside strings.
I usually add about 1.5 to 2 mm mm to this dimension and it seems to work our perfect for my guitars. So if you have an inset of 3 mm at the nut, you would have an inset of 4.5 to 5.0 mm at the 12th fret. This dimension is another one that should be discussed with your client your customer.
A Final Word:
Why all this fuss about fretboard width? As a player for more years than I would care to admit, besides tone and action, one of the most important aspects I consider for a fine guitar is the fretboard width at the nut and the saddle. Keep this in mind and the sensitivities of the guitar picker and you will have a happy customer or be very pleased with your very own guitar. It is details like these that make the difference from a factory made or production guitar to a fine hand crafted instrument.