When you’re shopping for a guitar or bass, one of the dimensions you’ll be presented with is an instrument’sfingerboard radius. What is that? How is it measured, and why is it important?
The fingerboard radius is the measure of the arc of the fingerboard across its width. You don’t have to look too closely at most electric guitar and bass fingerboards to see that few if any of them are truly flat; most of them have a slight convex curvature across their width. The fingerboard radius is the measure of that curvature.
Other types of stringed instruments don’t have these “radiused” fingerboards. Most classical guitars, resonator guitars, banjos, pedal steel guitars and some steel-string acoustic guitars, for example, have flat fingerboards.
The fingerboard radius measurement itself refers to the radius of a circle from which a small segment of the circumference equal to the width of the fingerboard is taken. The radius of the circle hence determines the amount of the fingerboard’s curvature (see diagram below). For example, if you take a circle with a 9.5” radius and remove a line segment from its circumference equal to the width of the fingerboard, you then have a 9.5” fingerboard radius (a common modern Fender spec).
If you take the same fingerboard width from the circumference of a circle with a larger radius, you now have a slightly flatter fingerboard radius. For example, a circle with a 12” radius yields a 12” fingerboard radius, which is slightly flatter than a 9.5” radius on a fingerboard of the same width. The lower the measurement, the greater the curvature, and vice versa.
Fingerboard radius is an important spec because it imparts a certain feel for the fretting hand; a certain character of comfortable playability. It’s a subjective measurement—there is no right or wrong degree of it, but there are several established conventions that players can choose among to suit their personal preferences. A smaller (more curved) radius is generally perceived as more comfortable for playing chords; a larger (less curved) radius is generally considered better for single-note playing and bending.
Fender has a few of its own well-established fingerboard radius conventions. These have evolved over the years, and a few different ones are available today that reflect various player preferences, such as vintage authenticity, modern playability and even specialized compound-radius designs in which the amount of curvature changes along the length of the fingerboard.