What is a Fingerboard Radius?

In a world where the specs of a guitar are combed over with a discerning eye, there is a long list of terms one must familiarize themselves with, and one that matters to many In-The-Know players is Fingerboard Radius. In simple terms, it is the curvature of the playing surface of a fingerboard.

"Oh, yeah that is suuuuuper helpful, Mathamagician!
Why don't you go learn some algebra, NERD?!" - Right Brain.

"Well, that's not productive, but maybe this will help?" - Left Brain.

The pic above and those below should help you get a line on how to get a read on the radius of a fingerboard. However, without measuring it via a radius block or the Plek Machine, we don't have any solid evidence we can rely on. In the shop, we use Radius Gauges for a rough reading and the Plek Machine once it's time to get dirty!

These radius gauges from Stew Mac do the trick for us!

Look at the edges of the gauges pictured above and notice how each of the 4 sides have a slight arc carved out of it. By resting the edge of the gauge against a fingerboard in a perpendicular fashion, we can determine which side of the radius block rests most securely against the fingerboard. Think of the Fretboard as a hill that slopes off evenly on both sides. A 7.25" gives us a steeper hill than any higher number. The flatter the fingerboard is, the bigger the circle, the higher the number, and the less steep the slopes are. On a lower number like 7.25", you have to push the string up the fret considerably more than you do on a 12". Once you get up to a 16", it's almost a horizontal push with a very little hill to climb, like you'll find on most Nylon String Guitars. 

Here is a 20" fretboard radius on a Taylor Nylon String Guitar... Made for huge bends :)

So now that we know where to look, what difference does it make? Well, this is a loaded question that requires a little history lesson to fully understand/appreciate, or a long-winded answer depending on how cynical you are. Settle in and read on to learn all you need to know about how a Fingerboard Radius affects the playability of your guitar! 

Going back to the early days of the electric guitar, most Fenders featured a 7.25" radius, at least on paper. Meaning that in the days of everything being done by hand, tolerances were exceptionally loose, especially compared to today's CNC Standards. The Blackguard Book (the Bible for early Tele enthusiasts) has also shown some early Tele's were closer to a 9.5" making the "vintage" conversation a little murky. When refretting guitars with our Plek Machine, we get multiple measurements of the fingerboard radius up and down the board and have seen the radius be off from spec by multiple inches sometimes, with Vintage Guitars being some of the worst offenders! I will never forget seeing a $40K Vintage Strat with a radius in the low 6's. With considerable arc on the fret with a 7.25" radius along with Vintage Frets being so small, it's not often you find a Vintage Fender in original condition that plays worth a darn!

Check a look at the 7.25" on this Masterbuilt '60s Strat...

And compare it to the 9.5" on this one!

Gibson has used 10" and 12" radius throughout the years, and some 16" on acoustics, giving them a flatter feel than most Fender Guitars. The radius, teamed with the shorter 24.75" Gibson scale, are two reasons why when strung with the same gauge strings, a Gibson has an easier feel than a Fender for most players (unless you have that Left Hand Kung-Fu Death Grip, in which case RELAX!). In other words, bending on a Gibson can (usually) be done with a lighter touch and is met with less resistance on the way up the bend. 

Here is a close look at a 12" radius on a 2020 Gibson SG...

While Gibson continues to use the 10"-12" on most electrics, Fender has long since acknowledged that modifying the fingerboard radius will change the left-hand experience. We have been ordering Fender Custom Shop guitars with radius ranging from 7.25" for the vintage enthusiast, to 9.5" for the typical modern player, to a compound radius in which the radius flattens out as the frets climb for those who use every fret of their guitar. 

An easy to understand drawing of a compound fingerboard radius...

Many Fender USA Products have adopted a flatter than Vintage radius, for instance, the Eric Johnson Strat comes with a 12" radius. A Compound Radius is the perfect choice for the player who explores the entire fingerboard with large bends, vibrato, open chords, bar chords, literally every position on every fret. 

The 10"-14" Compound Radius of the American Ultra Stratocaster...

Many brands like Charvel, Jackson, Ibanez, and other Super Strat Style manufacturers have been hip to the added playability a flatter-than-rounder-radius provides for decades. Add some big frets, or a Compound Radius into the mix and large bends don't choke out, vibrato is achieved with a light touch, and the guitar just feels faster. Even Vintage-Minded-Players are blown away with the Fender Ultra Series and how easy the necks plays thanks to the fret size and compound radius.

Some players still prefer a 7.25" especially for playing cowboy chords and lower position bar chords. This more curved fingerboard seems to be a natural fit for the more chordal player, however playing above the 5th to 7th frets on these guitars can prove tough, especially when it comes time to solo. Without a perfect setup and well-adjusted neck, bending on these guitars can be frustrating, with them choking out, getting buzzy, or not producing any pitch.

Fender's image for describing radius sure makes it easy to understand!
Check out their article on Fretboard Radius for another perspective.

Somewhere in the neighborhood of 9.5" to 12" seems to be perfect for the typical rhythm and lead player. Today, we don't just play in one position and need our guitars to perform equally well above and below the 12th fret. And that's where a Compound Radius dominates the conversation.

A 12" sits at the end of this Compound Radius-ed Custom Shop Strat...

The compound radius allows for next-level performance and is something you'll experience on instruments made for more demanding players. I have found a compound radius to (almost always, barring setup and personal preferences) guarantee a better playing experience. Granted, this is just my opinion and my favorite neck of all time runs a little less than 12" from the nut to the butt (thanks, Plek Machine!) but with a compound radius, I can be sure that bends get EASIER the higher I climb. And when you are shortening the string by fretting, the bending of a shorter string gets a bit rough on the left hand. Less resistance up high means easier bends!  

So now that we know that fretboard radius is a measurement of the arc of the fingerboard, here are a few Rule's-of-Index-Finger (because they aren't quite as reliable as the thumb).

• Classical Guitars have a flat radius, there is no curvature
• Martin Acoustic Guitars are typically a 16". A nice flat feel for a steel string.
• Gibson Electric and Acoustic Guitars run from 10" to 12".
• Most Taylor Acoustic Guitars have a 15" radius. Nylon gets a 20".
• Most Gretsch Electric and Acoustics from 9.5" or 12".
• Most PRS Guitars are 10" to 11.5".

This beautiful PRS Private Stock sports an 11" fretboard radius...

Wrapping up...
With Fingerboard Radius, it truly is a matter of personal preference. I have typically preferred an 11" or 12" but when Fender made the MIM Monterey Strat with an all-vintage-spec neck, I had to rethink my thunks! Even with a 7.25" fretboard radius and Vintage Frets, that is still one of the most confounding-ly playable guitars I have ever laid my hands on! We have also had many people insist they need a specific radius only to discover they liked something else just as much if not more! It's really easy to get hung up on specs in an attempt to find My perfect. However, what's perfect can change with your mood, literally. I guess my point is that if the specs of a guitar where prioritized behind how good it actually plays or sounds regardless of it's specs, we as players would find more instruments worthy and suitable. If I have learned anything about ordering Custom Guitars in the last 20 years, it's that just because it says something on a spec sheet A: doesn't make it 100% accurate and B: doesn't mean you'll enjoy playing it. 

So head to your local Mom-n-Pop to play a bunch of guitars with your new-found expertise on fingerboard radius! Now that you know what to pay attention to, you may just notice your preferences evolve too!

This installment of Matt's Blog was penned by Mathew Jenkins: guitar-nerd, ist, designer, teacher, assembler, and addict.