In creating and evaluating new guitar kits, the question of scale length comes up often. As a long time player and a kit builder, my understanding of scale length has evolved over time. As it turns out, it hasn’t been easy to get to the truth because there is a lot of false information floating around online, even from what appear to be reputable sources and experienced builders. Here are some details I have learned lately that I would like to pass on:
Myth: Scale length is the measurement from to nut to the bridge
Fact: Not necessarily. Scale length is the measurement from the nut to the 12th fret, x 2.
The reality is that the measurement from the 12th fret to the bridge is often about 1/16″ to 1/8″ longer than the distance from the nut to the 12th fret. The reason for this is pretty simple, and is key to the intonation and setup of your guitar. Just how much longer depends on a couple factors, such as the string, the scale, the style of guitar, and the height of the action.
As a string is fretted, it increases the tension and thereby sharpens the note. The distance between the fret and the bridge needs to be longer to keep the note in tune. This is why guitar bridges have a slant to them when installed.
So when you unwrap your new guitar kit, don’t be alarmed to find the measurement between the 12th fret and the bridge to be longer than the measurement from the nut to the 12th fret. Chances are it is exactly where it should be (assuming the neck is in the right spot!) And if you go in for a professional setup and are told otherwise, I suggest getting a second opinion just to be sure.
For more details on this concept and more math than I personally understand, check out this great article from LMII.com