In This Guide
1 What Intonation Is and Why It Matters
Intonation refers to the accuracy of your guitar's tuning across the entire fretboard. A guitar with good intonation plays in tune at every fret position, from the open string to the highest fret. A guitar with poor intonation may be perfectly tuned on the open strings but sound increasingly out of tune as you play higher up the neck, making chords and melodies sound sour and unpleasant.
The reason intonation needs to be set is that pressing a string down to a fret stretches it slightly, which raises its pitch. The amount of stretch depends on the string height, string gauge, and the distance the string must travel to contact the fret. To compensate for this pitch sharpening, the saddle is positioned so that the vibrating length of each string is slightly longer than the theoretical scale length. This compensation ensures that the fretted pitch matches the correct note.
If you have ever played a chord that sounded fine in one position but wrong in another, or if barre chords always sound slightly off no matter how well you fret them, poor intonation is very likely the cause. Setting intonation is the final step in a proper guitar setup, performed after adjusting the truss rod and bridge height.
Every guitar is a compromise. The equal temperament tuning system that frets are based on is itself an approximation, and no fretted instrument can be perfectly in tune at every position. But a properly intonated guitar comes close enough that your ear will not notice the tiny imperfections. A poorly intonated guitar, on the other hand, will sound noticeably wrong.
Pro Tip
If your guitar sounds out of tune even after you carefully tune the open strings, check the intonation before buying a new tuner. The problem is almost certainly the guitar's setup, not your tuner or your ears.
2 How to Check Your Intonation
Checking intonation is simple and requires only a reliable chromatic tuner. A clip-on tuner works, but a pedal tuner or a tuner app with a cent display is more precise because you need to see exactly how many cents sharp or flat each note is. Intonation adjustments are measured in cents, where 100 cents equals one half step.
Start by tuning your guitar accurately with fresh or reasonably new strings. Old, worn strings have uneven mass distribution and will never intonate properly regardless of saddle position. If your strings are more than a few weeks old, change them before attempting intonation work.
For each string, play the 12th-fret harmonic (lightly touch the string directly above the 12th fret and pluck it) and note the tuner reading. Then, fret the note normally at the 12th fret with your usual amount of finger pressure and check the tuner again. The two readings should match. If the fretted note is sharp compared to the harmonic, the string is too short and the saddle needs to move away from the neck. If the fretted note is flat, the string is too long and the saddle needs to move toward the neck.
Check all six strings. It is common for some strings to be perfectly intonated while others are off, because each string has a different thickness and tension. The wound strings (low E, A, D) and the plain strings (G, B, high E) behave differently, and the G string is often the most problematic because it is the thickest unwound string (or the thinnest wound string, depending on the set).
3 Tools You Will Need
For electric guitar intonation, you need a screwdriver (Phillips or flathead, depending on your bridge) to turn the intonation screws on the bridge saddles. Some bridges use Allen bolts instead of screws, so have a set of Allen keys ready as well. A chromatic tuner with cent accuracy is essential; you cannot do this by ear with reliable results.
You also need patience and a quiet environment. Intonation is measured in very small pitch deviations (a few cents), and background noise or rushing through the process leads to inaccurate results. Sit in a quiet room, mute any amplifiers, and take your time with each string.
For acoustic guitar intonation, the tools are different because acoustic saddles are not adjustable with screws. If the intonation is off on an acoustic, the saddle itself needs to be reshaped or repositioned, which requires fine files, sandpaper, and ideally a compensated saddle blank. This is a more advanced procedure best handled by a luthier.
Before starting, make sure your neck relief and action height are already set correctly. Intonation is always the last step in a setup because both relief and action height affect the amount of string stretch when fretting, which directly influences intonation. Setting intonation before the other adjustments means you will just have to redo it.
4 Setting Intonation on an Electric Guitar
On most electric guitar bridges (Stratocaster tremolo, tune-o-matic, hardtail, etc.), each string has its own saddle that can be moved forward or backward using an intonation screw. The screw is typically located at the back of the bridge and is accessible with a screwdriver or Allen key. Moving the saddle changes the vibrating length of the string.
Start with the low E string. Tune it precisely to pitch using your tuner. Play the 12th-fret harmonic and note the reading. Then fret the 12th fret normally and check the reading. If the fretted note is sharp, the saddle needs to move back (away from the neck), making the string longer. Turn the intonation screw to move the saddle back a small amount, retune the open string, and check the 12th fret again.
If the fretted note is flat, the saddle needs to move forward (toward the neck), making the string shorter. Adjust, retune, and recheck. This is an iterative process: adjust, tune, check, repeat. Each saddle movement changes the open string pitch, so you must retune between every adjustment. Take your time; rushing leads to inaccurate results.
Work through all six strings one at a time. The goal is to get each fretted 12th-fret note within one to two cents of the 12th-fret harmonic. Absolute perfection (zero cents difference) is ideal but not always achievable due to slight variations in string construction and fret placement. If you can get every string within two cents, your guitar will sound well intonated in any position on the neck.
Pro Tip
When fretting the 12th fret to check intonation, use your normal playing pressure. Pressing too hard will bend the string sharp and give you a false reading. Play the note exactly as you would during normal playing for the most accurate result.
5 Intonation on Acoustic Guitars
Acoustic guitar intonation is inherently less adjustable than electric guitar intonation because most acoustic bridges have a single saddle rather than individually adjustable saddles. The intonation is primarily determined by the saddle's position, angle, and profile (the shape of its top surface), all of which are set at the factory.
Many quality acoustic guitars come with a compensated saddle, which has a stepped or angled top profile that effectively gives different strings slightly different vibrating lengths. This compensation is calculated based on standard string gauges and provides good intonation for most playing situations. If you change to a significantly different string gauge, the compensation may no longer be optimal.
If your acoustic guitar has noticeable intonation problems, the options are limited compared to electric guitars. A luthier can shape or replace the saddle to improve compensation, adjust the saddle slot position (a more involved procedure), or install a compensated saddle designed for your specific string gauge. These are precision modifications that require experience and specialized tools.
For acoustic guitar players, the best approach to intonation is prevention: use the string gauge the guitar was designed for, maintain proper humidity levels to prevent structural changes, and have the guitar professionally set up if intonation problems develop. Minor intonation imperfections are normal on acoustics and are part of the instrument's character.
6 Troubleshooting Persistent Intonation Problems
If you have set the intonation carefully but certain strings still will not intonate properly, there are several possible causes. Old or defective strings are the most common culprit. A string with uneven winding, a kink, or corrosion will have inconsistent mass along its length, making accurate intonation impossible. Always intonate with fresh strings.
Worn or uneven frets can also cause intonation problems. If a fret has a groove worn into it from years of playing, the string contacts the fret at a slightly different point than intended, altering the effective string length. Fret wear is most common in the first five positions. A fret level and crown procedure by a technician restores the frets to uniform height and shape.
A poorly cut nut can cause intonation to be off in the lowest positions even when the 12th fret checks out correctly. If the nut slots are too high, pressing down at the first few frets stretches the string excessively, making those notes sharp. This is particularly noticeable on open chords that mix open strings with fretted notes in the first position. Proper nut height is an essential part of the overall setup.
Finally, heavy fretting pressure will always pull notes sharp, regardless of how perfectly the guitar is intonated. If you are pressing down much harder than necessary, you are bending the string out of tune. Developing a light, efficient fretting technique is as important for playing in tune as having a well-set-up guitar. If you notice your playing always sounds slightly sharp, try relaxing your fretting hand and using the minimum pressure needed to produce a clean note.
Pro Tip
The G string is notorious for intonation problems because it sits at the transition between wound and plain strings. Some players use a wound G string for better intonation at the expense of a slightly different feel. If your G string consistently refuses to intonate well, try a wound G or a different brand of strings.
Key Takeaways
- Intonation determines whether your guitar plays in tune at every fret position, not just the open strings
- Check intonation by comparing the 12th-fret harmonic to the fretted 12th-fret note on each string
- Sharp at the 12th fret means the saddle needs to move back; flat means it needs to move forward
- Always set neck relief and action before adjusting intonation; it is the last step in a setup
- Use fresh strings for intonation work; old or damaged strings will never intonate correctly
- Acoustic guitar intonation is limited to saddle shaping and is best handled by a professional