Guitar String Radius Gauges
All guitars, with the exception of classical guitars, have a slight radius on their fretboards. The radius gives the player a bit more comfort in playing. It also aids in the setup of the instrument. Over the last 60 years of modern guitar manufacturing, guitars have been made with all kinds of different fretboard radii. Each manufacturer seems to come up with a slightly different size radius. Some manufactures have used different radii for the same line of guitars of the years. Since fretboard and string radius is such an important part of guitar setup and playability, it is important to accurately measure the fretboard radius. That is where a string radius gauge comes in handy.
A string or fretboard radius gauge is either a square piece of plastic or metal that has different radii cut into each side. Since there are so many different common sizes of fretboard radius, string radius gauges generally come in a set of two squares. There are 8 different radii between the two square gauges. Measuring the fretboard radius is simple. Remove your guitar's strings and place your radius gauge on the fretboard. I usually like to place it between the 5th and 10th fret. Now shine a light behind the radius gauge. You will be able to see if the radius on the square matches the radius on the fretboard. If it doesn't simply turn the gauge until it fits smoothly on the fretboard without any gaps. That is the radius of your fretboard.
I have compiled this chart of all the most common fretboard radii that I have seen over the years. It is not an exhaustive chart, but it will show you the most popular sizes. Take a look.
|Modern Fender Stratocaster American guitar||9.5" (241 mm)|
|Vintage Fender Stratocaster guitar||7.25" (184.1 mm)|
|Gibson Les Paul guitar||12" (305 mm)|
|Gibson Sg guitar||12" (305 mm)|
|Ibanez guitars||12" (305 mm)|
|Jackson guitars||16" (406 mm) or compound, from 12" (nut) to 16" (heel). A compound radius is common on their newer models|
|Warmoth guitars Compound||from 10" (nut) to 16" (heel)|
|PRS Guitars Regular||10" (254 mm)|
|PRS Guitars Wide Fat and Wide Thin||11 11/16" (42.8 mm)|
|PRS Guitars 513||11 43/64" (42.4 mm)|
|PRS Guitars Hiland||11 21/32" (42 mm)|
|PRS Guitars Santana||11 1/2" (292 mm)|
|PRS Guitars Custom 22/12||11 1/2" (292 mm)|
|Most electric guitars with LSR roller nuts||9.5" to 10" (241 mm to 254 mm)|
|Most electric guitars with Floyd Rose bridge||10" (254 mm)|
|Traditional Classical guitars||flat (no radius)|
|Martin acoustic guitars||16" (406.4 mm)|
|Gibson acoustic guitars||12" (305 mm)|
Since a guitar's string radius must be set up to match the fretboard radius, it is nearly impossible to properly set up a guitar without accurately measuring the fretboard radius. This is why I think a set of string radius gauges is a must have in your guitar repair bench. These gauges are easy to use and easy to store. The best thing about these gauges is the price. I think I paid about $5.00 for my set of radius gauges. They look awesome and work great! Make sure to add these inexpensive string radius gauges to your guitar workshop today. If you would like more information about how to check your guitar string radius, please see my how to set a guitar's string radius article.