Guitar Tech Tips: Guitar Fretboard Radius Gauges

You don’t have to be a guitar tech nerd to benefit from a set of radius gauges.  Fret not (ha! a pun!), I’m not going to get all “tech mode” here.  But rather just check out a few common benefits for having some radius gauges on hand.  If you’re like me and a lot of other players, these numbers probably don’t mean all that much… just tell me if it feels right when you’re playing?  Know what I mean?

The very basic concept is that the numbers translate to that radius of a circle.  The curvature of the fretboard is based on the size of a big circle, so to speak.  A 16″ radius, like in the photo, would be based on a circle with a 16″ radius.  That’s considered to be a little on the flat side for guitar.  And you have the more “modern” Strat radius of 9.5″, which is like imagining a circle with a 9.5″ radius.  That’s a smaller circle than the 16″ radius, so the surface of the 9.5″ radius fretboard will be a little more curved and not as flat as the 16″.

So, you ask, why do I care?  Excellent question.  The basis of your fingerboard radius will determine other factors that can be dialed in for good feel and good sound.

Once you determine the radius, one of the more common uses is to confirm saddle height, as shown in the photo of the understring radius gauge.  Simply put, this helps nail a consistent string height across the fretboard.  The understring style is good for that, as measuring from below will be more accurate.  As you’ll see in the video below, a radius gauge also helps out on  TOM style saddles.

Going down to the other end of the fretboard, you can check your nut for accuracy in a similar fashion.  The nut can also be a culprit in playability issues ranging from improper setup to normal wear and tear.

Knowing your neck radius and using a radius gauge can help dial in some basic starting points for pickup pole piece adjustments.

If you are more technically inclined to work on your guitar, it’s obviously one of the best ways to know the proper radius block when giving the frets a tune up (ha!  another pun!).  Speaking of using a radius block, a set of radius gauges can also confirm the radius up and down the entire neck… you might discover you have a compound radius (one radius at the nut, gradually working to another radius at the higher frets) and you might prefer to use a range of radius blocks.  Better yet, you might have ordered a compound radius and could use some radius gauges to confirm you get what you paid for.

One of the simplest and best reasons to use radius gauges is so that you know what you have and what works for you.  While some players might be very adaptive from one guitar to another, you might be the Liam Neeson of guitars and have a very specific set of skills that requires a very specific set of needs.  Knowing these sorts of specs can be efficient and help ensure the best results when dealing with your guitar tech or your guitar repair shop.

Darth Phineas is a long time music industry insider who provides his readers with unbiased reviews on musical instrument and guitar gear. You can read more of his reviews and check out industry news on his Facebook community Darth Phineas, Twitter or his website is