What is the radius of your guitar’s fingerboard?
If this question is giving you flashbacks to high school math class, don’t worry. We’ll walk you through it.
Most guitar and bass fingerboards are not completely flat – they have a slight convex curvature.
The back of the guitar neck is even more rounded usually, making for a comfortable grip.
Measuring the Radius of Your Fretboard
As you probably remember from math class, the ‘radius’ is the distance from the center to the circumference (or edge) of a circle. To find the radius of a fingerboard, picture the fingerboard at the top of the circle and determine the arc from one edge to the other.
You can use a guitar under string radius gauge to determine the radius of your guitar’s fingerboard. If you don’t have one, you can simply use a piece of string.
To do this, find the fretboard’s centerpoint by measuring the distance between the nut and the 12th fret.
Then, place the string on the centerpoint, holding it down on the first and last fret. Measure the distance between the string and the 7th fret. This is the radius of the fretboard.
The smaller the measurement of the radius, the greater the curvature of the fingerboard.
The Why Behind Fretboard Designs
Fretboard radius is usually measured in inches, and the most common sizes on the market are 9.5”, 7.25” and 12”. Some go as high as 17” or 20”. The larger the radius the more “flat” the fretboard will feel. Smaller, more curved radius gives the guitar a comfortable grip and lets your finger curve naturally when playing bar chords. Vintage instruments such as vintage era Fender guitars use a radius as small as 7.5” which creates a classic comfort and feel that many players greatly appreciate today. Larger radius necks keep the feel of the neck more flat, which makes niceley for sweeping through arpeggios and scales across the strings. Many high performance, modern guitars use larger fretboard radius. However, the feel of the neck can be a little less comfortable for playing bar chords or having a relaxed grip on the neck.
Some guitars even use a compound-radius fretboard. This means that the fretboard radius will gradually change from a lower (more curved) to a higher (flatter) radius as you go from the nut to the heel of the neck.
There’s no hard-and-fast rules about which fingerboard radius is right for particular genres or playing style, however, the rounder fingerboards are usually well-suited for barre chords and flatter fingerboard radii gives a more even playing surface, ideal for string bending and sweeping.
You might not have realized it, but since the fretboard is curved, the strings don’t actually sit at the same height. Your strings are positioned at equal height above the fretboard, which means the string saddles need to match the curvature of your neck. The string saddles on many guitars have adjustable heights, which allow you to fix the action and ensure the strings match the curvature of the neck. If your guitar neck was perfectly flat (no radius), then the strings would sit at the same height, but there are no guitars with flat necks (that we know of!)