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What is intonation?

What is the best way to check my intonation and fix it if necessary?

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Intonation refers to the instrument being in tune along the fretboard.

An easy way to check the basic intonation of a guitar is to hit a 12th fret harmonic and compare the pitch with a note fretted at the 12th fret.

If the fretted note is sharp, the string needs to be lengthened.

If the fretted note is flat, the string needs to be shortened.

The length of the strings can usually be adjusted at the bridge of electric guitars and basses.

Tune each string to pitch before checking its intonation.

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Intonation is all about notes being in tune along the fretboard. Frets are straight, so your guitar is pretty much always a little bit out of tune at any point down the fretboard. This is the reason you have compensation at the bridge and often the nut too. (Have a look at the bridge, the strings aren't all fixed at the same distance from the nut.)

Some companies have tried to address this by not having straight frets. I believe Steve Vai has messed around with this.

True Temperament Fretting System

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    Let's say a guitar with an even temperament has the intonation problems spread evenly across the length of the string, as with any tempered instrument. The intonation problem itself is a bit different. (I know you know, but I found your answer a bit misleading)
    – Pif
    Commented Jan 13, 2011 at 22:27
  • In practice I think people with standard guitars tend to develop tuning habits that put their instruments in tuning for specific songs. A lot of touring guitarists have a rack of several guitars that they use on stage, and I wouldn't be surprised if there are slight differences in each's intonation (the ones with talented roadies anyway)
    – Darren Ringer
    Commented Oct 23, 2014 at 12:57
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intonation refers to your guitar being in tune at various points across the fretboard. To tell if your guitar has correct intonation, check the tuning at various points on the fretboard, most commonly the 12th fret, to make sure notes are in tune there as well as with open strings.

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  • "Various points across the fretboard" need to be strong harmonics that match the frequency of the note when fretted, which basically rules out everywhere except the 12th fret which should be the same pitch as a harmonic and when fretted.
    – Anonymous
    Commented Jan 14, 2011 at 15:21
  • The 19th fret is also available on most guitars, and certainly on all electric guitars.This gives a 5th harmonic, e.g. a B note on the E strings. Some guitars also sport a 24th fret, giving an octave note/harmonic.
    – Tim
    Commented Jul 24, 2013 at 9:35
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Intonation is pitch accuracy, whether it's a person's intonation or an instrument's intonation. When your guitar is tuned correctly, then it has the correct intonation. See here for ways to tune your guitar:

How do you tune your guitar?

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  • Actually, in a "guitar context", "intonation" refers more specifically to "being in tune" for the fretted notes. In your answer, you imply that "being in tune" and "being with correct intonation" are the same thing, and the same thing they are not.
    – Rafael Almeida
    Commented Jan 13, 2011 at 22:14
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    Instrument intonation does take more factors into account, but the basic definition of intonation is 'being in tune.' He actually asked two questions with the original post.
    – Anonymous
    Commented Jan 14, 2011 at 13:53
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On a steel string acoustic you really have to trust that the manufacturers mathematics and building techniques have got the scale length correct. The frets in the correct location and the bridge saddle in the right place and at the correct angle. Then it can vary with string guage and the guitars set up. Now add the players techniquie and the word Compromise enters the equation..Don't always think that because a guitar has a brand name on it all of the above is correct. Electrics do offer Intonation adjustments ussually on every string or pairs of strings...Always check Scale length.. Measure from the Nut face to the crown of the 12th fret, then double it. Not all but a lot of Gibson guitars 24.75 inch scale length has crept to around 24.6 over the years and dependent on the factory. Your aim is to have your guitar when tuned to sound in tune and pleasant, whether playing open chords, bar chords with or without a capo.

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I use a Korg Orchestral Tuner to test all the open strings and frets. Just for curiosity I took off all the frets and made small brass frets for every note on the guitar. I glued them on with Bostik Contact Glue. The frets are 3mm thick with a thin brass base about 1/4 inch square . Also just for curiosity they are all tuned to Kirnberger 111. And it works too .

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  • The frets are not dead in line across the fretboard obviously but it`s not a problem .Interestingly ,the octaves are not dead in line either but they are accurately in tune . This tuning takes account of string stretching .
    – john cadd
    Commented Sep 21, 2016 at 23:30
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I use a guitar tuner to do this, firstly make sure all your open strings are in tune, then play an open harmonic at the twelve fret and see if it's also in tune. The next part depends on the type of guitar you have. For a standard strat/super strat guitar you want to bring the saddle forward using the screw slightly then check the harmonic again, if it's flat you need to bring the saddle backward. There's a good youtube video here:

http://www.youtube.com/watch?v=GZVRCMJLnm4

This isn't the ONLY reason your guitar could be intonated incorrectly though.

More info here:

http://www.fretnotguitarrepair.com/repair/electric-guitar/intonation.php

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  • When the open string is in tune, the 12th fret harmonic will always be in tune ! Did you mean the FRETTED note at 12 ?
    – Tim
    Commented Jul 24, 2013 at 9:45
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My 2 cents : when you fret a note, you slightly change the vibrating length of the string; an harmonic at the 12th fret will be at the exact middle of the string, but the actual fretted note won't - think of a triangle formed by the open string, the vertical of the fret and the actual string being fretted.

When the fretted note goes flat, it goes flatter and flatter up the neck, and if sharp it goes sharper. If it's bad enough you can check it just by playing two notes an octave apart on the same string.

You can adjust the length of the string with a screw. On a fixed bridge, it's as simple as others have pointed out : check the high fretted notes with a tuner or the harmonics and fix.

With a floating bridge though, it's a bitch to setup, although depending on the model you have some very useful tools.

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To fix intonation (on an electric guitar), you'll need to adjust the screws on the bridge: alt text

This will lengthen or shorten the string enough to get the frets to sound in tune. More info

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The main adjustment to correct intonation is making sure the 12th fret is in tune when the guitar is tuned correctly. That's the first step, but that's not all.

(Don't use the 12th fret harmonic for intonation. Use the open string and the 12th fret. Just don't.)

The second adjustment is more tricky. The Rule of 18 (actually 17.835) is that the next fret is placed 1/18th (or so -- see previous digression) of the way between the previous fret (or the nut) and the bridge, and this would be wonderful, except for fretting. This math does not take into account the thickness of the string. This means that, unless you adjust to account for it, you could be perfectly in tune on the low E with an open string and fretted at the 12th fret, the G at the third fret will be sharp. There are a few ways to handle this. First, develop a lighter touch and stop bending the string so sharp when fretting. Second, sometimes people tune and intonate so the low E and A strings are a little flat but the strings play in tune at the 3rd and 12th frets. This is also one of the issues that Feiten tuning is supposed to handle.

For many guitarists, intonation is something you think about when you change strings, and adjust with a screwdriver. Intonation is ultimately about your ears knowing what notes they should be going for, and your hands knowing how to get them. By bending strings, the best players can play perfect notes on a poorly-built and badly-intonated instrument. I'm not perfect in this, but embarrassing experiences with a lap steel showed me how bad I was, and I'm trying to learn to be better.

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