Trying to measure your guitar’s scale length?
To calculate a guitar’s scale length, measure between the inside edge of the nut and the center of the 12th fret and then double the number.
Why Measure at the 12th fret?
It could be argued that the true scale length of a guitar is the distance the guitar string is suspended between two fixed points, as shown below.
However, the saddle on most guitars (excluding some classical guitars) is almost always placed at an angle.
As can be seen in the diagram below, doing so extends the length of the heavier gauge strings slightly, making measuring the distance between the nut and saddle inaccurate.
Why are Guitar Bridges Bridge Placed at an angle?
The saddle is placed at an angle to compensate for the heavier gauge strings’ additional mass which affects the string’s ability to vibrate and stretch, compared to the lighter gauge 1st and 2nd strings. If not compensated for this would otherwise affect the guitar’s intonation.
What is Intonation?
On the guitar, intonation describes the relative accuracy of pitch. For example, when you play the 1st string as an open string (unfretted) the note should also be E at the 12th fret, as this should be exactly one octave higher in pitch.
If, however, the intonation is not set correctly, the note played at the 12th fret will be flat or sharp compared to the open string. This makes notes and chords sound out of tune when played in higher positions on the neck.
Intonation is affected by several factors, including action and neck relief, along with the string’s ability to vibrate and its elasticity e.g. ability to stretch, both of which are affected by the string’s mass.
Keep in mind, that when notes are fretted, the guitar string is pushed down toward the fretboard, causing the string to stretch. Lighter gauge strings have greater elasticity than heavier gauge strings due to the string’s thicker core and subsequent higher tension.
When the string’s length is shortened in this way, the length of the string is reduced. This reduces the overall mass of the string which allows the string to vibrate faster, raising its pitch.
But, when the string is pressed against the fretboard the string also stretches, unlike when playing an open string.
It’s important to keep in mind, that the plating (the winds) on the heavier/thicker strings aren’t responsible for limiting the string’s ability to stretch. It is the string’s core that is responsible. The windings are used to add mass (which does affect the string’s ability to vibrate) without increasing the core size to the point where the string would have so much tension it would almost be impossible to stretch. Likewise, the lighter gauge strings are not wound, as the core size would therefore be so small that the strings would consistently break under tension.
The elasticity of the string will vary based on the core thickness of each string. However, between strings 1 and 6, the change in core thickness increases proportionally, except between the 2nd and 3rd strings which can be addressed using a compensated saddle, which we’ll discuss below.
In simple terms, all of this means the actual suspended length of each open string must be adjusted based on the physical properties of the string. To compensate for these factors, your saddle is positioned on an angle, which increases the length of the heavier, wound bass strings compared to the higher treble strings e.g. the E and B strings. The additional length the angle affords the lower heavier strings compensates for the additional mass of the strings.
However taking into account all the different factors listed above it is never an exact science, meaning your guitar is likely never 100% perfectly intonated.
Adjusting a guitar’s intonation is much easier on an electric guitar (with some exceptions) as each string is assigned an adjustable metal saddle.
When adjusted (by turning a spring-loaded screw at the rear of the saddle) the individual saddles move closer to the nut or further away, adjusting the length of the string.
Additional smaller screws can also be adjusted to raise the height of each saddle to compensate for the different thicknesses of each string.
In the image to the left, we can see that the individual saddle for the high E treble string is closer than the low E bass string. However, the first wound string is shorter than the 4th string is shorter than the 3rd string.
This is as outlined below in the compensated saddle section. The difference is the first wound string on electric guitars is the 4th string and not the 3rd string as seen on acoustic guitars.
The bridge shown in the image is a typical Fender Stratocaster bridge. Tune-O-Matic bridges, as seen on the Gibson Les Paul (and many other Gibsons) work differently, although the basic principles are the same.
While adjustable bridges have been toyed with on the acoustic guitar over the years, adding metal in any form to the soundboard (top) of an acoustic guitar will affect the soundboard’s ability to resonate, which indirectly affects tone, volume, and projection.
Hence, all good steel-string acoustic guitars feature an angled saddle which compensates for the properties of the guitar strings and differences in gauges.
One method guitar manufacturers (including Ibanez, Schecter, and even Paul Reed Smith), are using to get around this problem on select models, is multiscale guitars featuring fanned frets. While this idea dates back to the renaissance period it is enjoying somewhat of a resurgence.
When it comes to classical guitars, the saddle will be either completely straight or placed at just a slight angle on the guitar body.
This is because the difference in string tension caused by the difference in mass between the nylon high E and low E is not comparable to the differences in mass of electric and acoustic guitar strings. As a result, much less compensation is required.
Compensated saddles are used to fine-tune intonation.
A compensated saddle is a saddle that has sections removed so the point of contact for the string is changed, resulting in a fractional change to string length between the nut and saddle.
Many people wonder why the 2nd string (B string) is compensated seemingly more than the 3rd (G) string. The reason for this is the core diameter of both strings. While the wound string has greater mass due to the string being plated in bronze or brass, the core diameter is larger on the B string which affects the string’s ability to stretch.
Common Scale Lengths
Guitars come in different scale lengths and this affects string tension, which affects tone and playability. For example, Fender utilizes a 25.5-inch scale fretboard on their electric guitars. While Gibson utilizes a short scale 24.5″ scale length.
The small difference in scale length means the distance between frets is affected, affecting playability, and the string tension. For example, Gibson’s string tension, being a shorter scale length is lower, while Fender’s is usually higher.
Is this why Fender Guitars are usually credited with a brighter tone than Gibson? While it’s not the sole reason, it would contribute.
Otherwise shorter scale guitars, e.g. smaller guitars made for children tend to have a shorter scale length, while baritone guitars and extended scale guitars may utilize a scale length of up to 27″ and beyond.
While scale length itself is simple to measure (from inside of the nut to the center of the 12th fret) as can be seen through the use of angled and compensated saddles, not to mention other innovations such as multi-scale or fanned frets the scale length issue has long been a problem for many different types of guitar. This makes simply measuring the length of the string between the nut and saddle inaccurate.
Did you enjoy this article? Be sure to check out some of our other articles on the mechanics and physics of the acoustic guitar.