To many guitarists, intonation is a mysterious thing. Most guitarists know it has something to do with tuning, but many are not sure exactly what and fewer still know how to adjust the intonation of their guitar. In this article we will demystify intonation and give you a step by step process in making sure your guitar in intonated properly!

Intonation and Theory

The frets on a guitar are spaced so that the notes will be in tune as we play them, with each fret representing a half step for the string that you are playing. Tuning is done with open strings. Intonation is the guitars’ ability to stay in tune as the strings are played further up the neck. For instance, every 12 frets a note repeats itself. The top string is an ‘E’, and on the 12th fret it is also another ‘E’. The ‘E’ at the 12th fret is an octave higher, and if it is perfectly in tune then that string is properly intonated. When all the strings tune true in the open position and at the 12th fret, the guitar is intonated. If the tuning at the 12th fret is off on one or more strings, that means that the note formed there will either be sharp or flat. The higher up the neck you play either scales or chords, the more those scales and chords will begin sounding out of tune. This is especially true when you are playing above the 12th fret. Remember, 12 frets above your current position is always the same note, an octave higher. A ‘G’ on the third fret will also be a ‘G’ on the 15th fret. If the guitar is intonated properly, that higher note will tune true.

Check Your Action: The Neck and Bridge

There are several things that can affect your intonation, but the saddle is the most important part of your guitar when it comes to setting the intonation correctly. However, if the action and the neck of the guitar are not properly set up, it will be difficult or impossible to set the intonation correctly. The neck should be straight, or have a very slight forward bow to it. This forward bow is called ‘Relief’ and can be anywhere from 0.2 mm to 0.3 mm. This is a very slight bow, and is designed to give the strings room to vibrate without brushing against the higher frets. Action refers to how far from the neck the strings of the guitar are. At the nut of the guitar, the action is usually around 1.2 mm to 1.6mm (or around 3/64 of an inch). The action will also depend on the taste of the player. After making sure your action and the neck of the guitar are properly adjusted, we are ready to check our intonation!

Adjusting The Bridge

There are several types of bridges when it comes to the ability to adjust intonation; adjustable, compensated and non-compensated.

Non-Compensated
Non-Compensated
Compensated
Compensated

Most acoustic guitars are going to have a bone or plastic saddle, and they will be either compensated or non-compensated. You will notice on non-compensated saddles the strings cross the saddle in a straight line, although the saddle itself is usually set at a slight angle. On a compensated saddle, there are small variations in where the strings make contact with the saddle. This makes the string length to the nut slightly different lengths from the nut of the guitar, and it is these small differences which will make the guitar intonated or not.

Adjustable
Adjustable

On electric guitars, you will see that most bridges are constructed so that each string rests on an individual saddle. These saddles can be slid forward and backward through the use of a small set screw, usually at the back of the bridge. They can also be adjusted for height (this is where you can adjust the height of the action).

Check Each String At The 12th Fret

The next step is checking the tuning of each string at the 12th fret. After your neck is adjusted and your action is properly set, tune the guitar with the best tuner you have. Check the E in the open position, and then fret the E string at the 12th fret and check the tuning there. The way you adjust the saddle will be determined by whether the ‘E’ note at the 12th fret is sharp or flat compared to the open ‘E’ note.

  • If the note is sharp at the 12th fret, move the saddle towards the back of the guitar
  • If the note is flat at the 12th fret, move the saddle towards the front or the headstock of the guitar

These will be very small adjustments. Take it slow, and loosen or tighten the set screw 1 – 2 turns (this will move the saddle forwards or backwards – usually turning the set screw clockwise will move the saddle backwards). Then retune the string in the open position and once again check the tuning at the 12th fret. It may take several tries to get the balance perfect, but just keep remembering to retune the open string after each small saddle adjustment.

Perform this for each string, moving the saddle forwards or backwards with the set screw until the tuning at the 12th fret is true to the open note. And that is all there is to it – your guitar is now properly intonated, and your chords and lead runs should sound much better!

Unfortunately, with acoustic guitars it is much harder to set the intonation; the better the acoustic guitar is, the better its intonation will be as long as the proper saddle is being used and the neck is properly adjusted. A compensated saddle can be fitted to acoustic guitars that did not originally come with one – your local Sam Ash luthier can help with that or any other adjustments you need to make.

So the next time you tune your guitar, think about its intonation and check the tuning at the 12th fret. If your guitar is out of tune, follow the simple steps above! It only takes a few minutes, and the better you understand your guitar the more prepared you will be to make sure that your instrument sounds the best it can!