Setting guitar intonation - How to check it correctly
Why a perfectly tuned guitar can still sound out of tune
You tune your guitar perfectly—but chords or individual notes higher up the fretboard still sound somehow off?
If so, the problem might not be the tuning of the open strings, but rather the guitar's intonation.
A guitar's intonation is set correctly when the fretted note at the 12th fret is exactly one octave above the open string. If the note there is too sharp or too flat, the pitch changes more or less than intended when fretting.
This is especially noticeable with chords, double stops, and melodies in higher positions. The guitar is correctly tuned on the open strings, but sounds increasingly out of tune as you move up the fretboard.
So before you keep retuning constantly, it's worth checking if your guitar's intonation is set correctly.
Intonation and fret accuracy are not the same thing
The terms intonation and fret accuracy are often confused, but they describe two different things.
Fret accuracy is determined by the position of the frets. If the frets are placed correctly during construction, the fretted notes will be in the intended spots on the fretboard. You usually can't just adjust this on a finished guitar.
Intonation, on the other hand, can be corrected on many electric guitars and basses by adjusting the position of the individual string saddles at the bridge. This adjusts the vibrating length of each string.
To check it, you compare the pitch of the string's harmonic with the fretted note at the 12th fret. If the fretted note is too sharp or too flat, the effective string length must be corrected accordingly.
Correctly set intonation ensures that the guitar plays as in-tune as possible across the entire fretboard.
How to check your guitar's intonation
First, tune the string as accurately as possible. Then, play the natural harmonic at the 12th fret and check its pitch with a precise tuner.
Next, fret the same string at the 12th fret and compare the fretted note with the harmonic.
If the fretted note is sharp, the vibrating string length is too short. The saddle must be moved further away from the neck.
If the fretted note is flat, the vibrating string length is too long. The saddle must be moved toward the neck.
After every adjustment, retune the open string and repeat the measurement. Work in small steps until the harmonic and the fretted note at the 12th fret match as closely as possible.
When fretting, be careful not to press the string down harder than necessary. Too much finger pressure can pull the fretted note sharp and skew the measurement.
Why a precise tuner is important for intonation
Adjusting intonation often involves very small differences in pitch. A tuner that only roughly indicates whether a note is "right" isn't always enough.
It's important that you can see the deviation between the reference note and the fretted note as accurately as possible. Even a few cents can make a difference when checking intonation.
The manual Note Lock on the TUNE-O-MATIC holds the note being tuned, making it easier to check guitar intonation
It's especially practical if the tuner can hold the note you're checking. This prevents the display from constantly jumping to neighboring notes, allowing you to compare the harmonic and the fretted note specifically.
That's exactly why the TUNE-O-MATIC has a manual Note Lock. You can select a specific note and precisely observe the deviation while adjusting the intonation.
Setting intonation: Step by step
First, tune all your guitar strings accurately and hold the instrument in the playing position you normally use.
Start with one string and play the natural harmonic at the 12th fret. Check the pitch with the tuner.
Then, fret the same string at the 12th fret and compare the pitch.
If the fretted note is sharp, increase the vibrating string length by moving the saddle away from the pickups or the neck.
If the fretted note is flat, shorten the vibrating string length by moving the saddle toward the neck.
Retune the string after every adjustment and repeat the measurement. Even small changes to the saddle can significantly affect the intonation.
Work your way through the instrument string by string, and finally check all strings one last time. Because of changes to the bridge or individual saddles, it can be useful to repeat the measurements a second time.
When you should check your guitar's intonation
You should always check the intonation whenever important conditions on your guitar change.
A new setup may be necessary, especially after changing string gauge. Thicker or thinner strings react differently and can change the intonation.
It's also worth checking when switching to an alternate tuning. For example, if you permanently switch from standard tuning to Drop D or a lower tuning, the string tension and feel will change.
You should also check the intonation after major work on the instrument—such as adjustments to the neck relief, action, or bridge.
And of course: if the open strings are perfectly tuned but chords or melodies in higher positions still sound noticeably off, checking the intonation is a good idea.
Clean intonation starts with precise checking
A guitar can be perfectly tuned on the open strings and still sound out of tune in higher positions. That's exactly why checking the intonation is part of a proper guitar setup.
Compare the natural harmonic and the fretted note at the 12th fret, work in small steps during adjustment, and retune the string after every change.
With a precise guitar tuner, you can detect even small deviations and check the intonation of each string specifically.
The TUNE-O-MATIC supports you with chromatic note detection and a manual Note Lock. This keeps the display focused on the note being tested, allowing you to precisely set your guitar's intonation.