One of the first things you notice when you grab a guitar neck is the rounded shape, which accommodates the natural curve of your hand. You’ll also notice that the shape of the back of the neck, where your palm fits, is different than the front of the neck — the fingerboard. Typically, the fingerboard side is flatter, but it has a convex arc. The shape of that arc is the fingerboard radius (sometimes called fretboard radius). Fingerboard radius is the curvature of the fingerboard across the neck, from the lowest string to the highest string, and just like the radius of a circle, it can be described by a number.
The exact shape of that arc, from rounder to flatter, is expressed numerically in inches or millimeters. For example, if you’ve ever seen the specs for an electric guitar neck, you might have read 7.25-inch as the radius. The way that number is derived is by drawing a circle with a 7.25-inch radius — remember, “radius” is a straight line from the center to the circumference of a circle — and placing the fingerboard at the top of the circle (Figure 1). The arc from one edge of the fingerboard to the other edge creates the 7.25-inch fingerboard radius.
To see what a different size fingerboard radius looks like, take the same fingerboard, and place it inside a circle with a different radius. The neck on the right (Fig. 1) above uses a 16-inch radius. Since the circle is larger, the resulting arc across the fingerboard is flatter — because the width of the fingerboard is the same. Other common sizes for fretboard radius are 9.5-inch, 10-inch, and 12-inch. The higher the number, the flatter the fingerboard.
From a guitarist’s viewpoint, fingerboard radius has to do with feel and playability and is completely subjective; no radius is better or worse. It’s a personal choice that has to do with fitting your hand and playing style. A rounder fingerboard radius tends to fit the natural, relaxed curve of your fingers, which is great for playing in lower neck positions, chords, and barre chords anywhere on the neck. A flatter radius gives a more consistent and even playing surface, which is great for string bending and moving quickly and efficiently across the fingerboard vertically, especially in higher positions.
For historical perspective, Fender guitars from the 1960s had a 7.25-inch radius, and solidbody Gibsons from the same time had a 12-inch radius. In the 1980s, “shredder” guitars like Ibanez, Charvel, and Jackson had adopted a 16-inch radius. In that same time period, Fender added a 9.5-inch radius, and PRS guitars were mostly 10-inch. More recently, radii come in all sizes, for all manner of applications. Most manufacturers have a few standard sizes they adhere to, but exceptions are plentiful. Another modern option is a compound-radius (Fig. 2), where the area closer to the nut is rounder, and the fingerboard flattens out as you move toward the heel (closer to the body). A common compound-radius offering is 12-inch – 16-inch.
Other Fretboard Radius Options
The electric guitar is really the only stringed instrument that offers multiple fretboard radius options. Classical guitars traditionally have no radius whatsoever. Martin acoustic guitars have had a 16-inch radius dating back to the 1930s. Electric basses have some variety, but it’s not a feature that is called out. If you take a straw poll and ask your bass player friends what their favorite fingerboard radius is, you’re likely to get an answer like, “the one that’s on my favorite bass.” No, that’s not a bass-player joke; it just drives home the fact that fingerboard radius is the electric guitarist’s domain.
If you are someone with small hands, you may prefer a smaller radius, such as 9.5 inches. While someone with bigger hands may prefer a larger radius, such as 16 inches.
The most important thing to remember about fingerboard radius is that it is one aspect of many that contributes to the overall feel of a guitar. I personally prefer a radius that falls in the middle of the standard list, 9.5-inch – 10-inch, but have been surprised by guitars with a flatter or rounder radius. The overall design of a guitar creates its feel, and radius is just one component. Whatever radius feels right is the right radius for you.
If you’d like to learn more about the different parts of the guitar and what you should look for in buying your first or next instrument, check out our Best Electric Guitars for Beginners and Best Acoustic Guitars for Beginners articles!