Guitar Dictionary Category
Guitar Anatomy & Setup
What Is Guitar Intonation?
Guitar intonation is the accuracy of the fretted pitches across the neck after the open strings have been tuned. A guitar can have perfectly tuned open strings and still sound sharp or flat when chords and notes are played higher on the fretboard.
Intonation is adjusted mainly by changing each string’s effective length at the saddle. Pressing a string to a fret stretches it slightly and raises its pitch, so the saddle position is compensated beyond the simple scale-length measurement.
Tuning and Intonation Are Different
Tuning sets the pitch of the open strings. Intonation determines whether the fret positions continue producing the intended notes. A guitar tuner can test both, but turning the tuning machines does not correct a poorly positioned saddle or inaccurate fret placement.
Temperament also matters. A standard fretted guitar uses equal-tempered fret positions, so every chord is a practical compromise rather than a collection of acoustically perfect intervals. Intonation aims for a useful balance across the neck, not mathematical perfection in every chord shape.
How to Check Guitar Intonation
Install reasonably fresh strings, tune the open string accurately and compare the 12th-fret harmonic with the note fretted at the 12th fret. Use the normal fretting pressure required to sound the note. Pressing too hard can bend the string sharp and create a false reading.
On an adjustable electric-guitar bridge, a fretted note that is sharp usually requires a longer string length, moving the saddle away from the nut. A flat fretted note usually requires a shorter length, moving the saddle toward the nut. Retune the open string after every saddle movement and repeat the comparison.
Why Intonation Changes
Old or damaged strings can intonate unpredictably. A different string gauge, altered tuning, high action, excessive neck relief, a poorly cut nut or a moved floating bridge can change the result. On handmade instruments, inaccurate fret placement or scale-length measurement can create problems that saddle adjustment cannot fully correct.
Acoustic guitars usually have a fixed saddle with limited adjustment. Compensation may require shaping or replacing the saddle, and a structural or fret-placement problem requires professional diagnosis.
Intonation and Playing Technique
Even a well-adjusted guitar can sound sharp when the player squeezes too hard, bends a string sideways during a chord or places a capo with excessive pressure. Tune and test with the same touch used in normal playing. Check both single notes and common chord shapes because the practical goal is musical agreement across the instrument.
Why Intonation Matters
Poor intonation becomes more obvious as the player moves up the neck or records doubled guitar parts. Accurate intonation helps chords, melodies and harmonics agree with one another and with other instruments. It is one of the main reasons a complete setup should be evaluated as a system rather than as a collection of isolated adjustments.
Kalymi Tip
In Kalymi Music’s cigar box guitar buying guide, I recommend tuning each string open and then checking it again at the 12th fret. Do this for every string. It quickly reveals whether the instrument remains in tune across the scale instead of merely producing correct open notes.
Use fresh strings and a light, repeatable fretting touch before adjusting anything. If the 12th-fret note changes substantially when you press harder, part of the problem is technique or excessively high action. If every string is wrong in a similar way on a handmade instrument, bridge position or fret placement may be involved.
For a movable cigar box guitar bridge, mark the correct location after the intonation is set. For a fixed acoustic saddle or a problem that cannot be corrected within the bridge’s adjustment range, have a repair technician diagnose the complete setup.
Related Terms
Learn More
- What to Look for When Buying a Cigar Box Guitar
- Introduction to the Two-String Cigar Box Guitar
- Learn Purple Haze on Cigar Box Guitar
- Which Instrument Should You Learn First?
- Cigar Box Guitar Learning Path
- Guitar Learning Path
Reviewed by
Brent C. Robitaille,
music educator and founder of
Kalymi Music.