How to Set Guitar Intonation — Complete Step-by-Step Guide

If your guitar sounds in tune on open strings but increasingly out of tune the higher you go on the neck, the problem is almost certainly intonation. Intonation is one of the most common setup issues on guitars, and one of the easiest to fix once you understand the principle.

This guide explains what intonation is, how to check it, and how to adjust it on the most common bridge types.

What Is Intonation?

Intonation refers to whether each note on the guitar plays at the correct pitch as you move up the fretboard. A guitar with perfect intonation plays in tune at every fret. A guitar with poor intonation plays in tune on the open strings but goes sharp or flat at higher positions.

The physics: The relationship between string length and pitch is not linear — a longer string vibrates more slowly and produces a lower pitch. When you press a string down at a fret, you are effectively shortening the string. The position of the bridge saddle determines the exact total string length. If the saddle is in the wrong position, the fretted notes will not divide the string correctly, and they will be out of tune.

Why the 12th fret matters: The 12th fret should produce exactly the octave of the open string. If you play the open E string (low), the 12th fret should produce an E exactly one octave higher — the same note, 12 semitones up. If it is even slightly off, the intonation is wrong.

What You Need

• A reliable chromatic tuner (a clip-on tuner, pedal tuner, or tuner app that responds accurately to individual string pitch)
• A small screwdriver (Phillips or flathead, depending on your bridge)
• A capo (optional but helpful)
• Fresh strings (new strings make intonation more stable — do not bother setting intonation on old strings)

Step 1: Change Your Strings First

Old strings lose elasticity and intonation stability. If your strings are more than 4–6 weeks old, change them before setting intonation. Intonation set on old strings will be wrong when you put on new strings.

Allow new strings to stretch for 30–60 minutes of play before tuning precisely.

Step 2: Tune the Guitar to Concert Pitch

Use an accurate tuner and tune every string to standard pitch (E A D G B E). Every string must be perfectly in tune before you start checking intonation.

If the neck has a bow (too much relief or backbow), the intonation will be affected — address the truss rod before intonation if needed, though this is a separate adjustment.

Step 3: Check the 12th Fret Harmonic

Play the natural harmonic at the 12th fret. Touch the string lightly directly over the 12th fret wire (do not press down), then pluck the string. The string will produce a clear, bell-like tone. Check this against your tuner — this is the reference pitch for that string's octave.

The 12th fret harmonic should be the same as the open string, but one octave higher. If it is not, your tuner or string is the problem, not the intonation.

Step 4: Check the 12th Fret Fretted Note

Now press down the string at the 12th fret (fret it normally) and pluck the string. Check this note against your tuner.

Compare the harmonic and the fretted note:

• If they are identical — intonation is correct for that string
• If the fretted note is sharp — the string is too short. You need to move the saddle back (away from the neck) to lengthen the string
• If the fretted note is flat — the string is too long. You need to move the saddle forward (toward the neck) to shorten the string

The phrase to remember: "Sharp? Move it back. Flat? Move it forward."

Step 5: Adjust the Saddle

This is the mechanical step. Different bridge types have different adjustment mechanisms:

Fender Stratocaster (standard tremolo)

Each saddle on a Strat bridge has a single Phillips head screw pointing toward the back of the guitar. Turn this screw to move the saddle forward or back.

• Sharp fretted note: Turn the screw clockwise to move the saddle back (extending string length)
• Flat fretted note: Turn the screw counter-clockwise to move the saddle forward (shortening string length)

Important: After moving the saddle, the open string pitch will shift slightly. Retune the open string before checking the 12th fret again.

Gibson Les Paul (Tune-O-Matic bridge)

The Tune-O-Matic bridge has individual saddles that slide in a slot. Each saddle is adjusted by turning a screw on the side or back of the bridge with a flathead screwdriver.

The movement direction varies by model — consult your guitar's documentation or simply try turning and observe whether the saddle moves forward or back.

The principle is the same: sharp = saddle back, flat = saddle forward.

Fender Telecaster

Vintage Tele bridges have three saddles (two strings per saddle). This makes true per-string intonation impossible — the compromise is to set the intonation for each saddle to the average of the two strings it carries.

Modern Telecasters and aftermarket bridges have six individual saddles, allowing proper per-string intonation.

The adjustment screw is similar to the Strat: one Phillips screw per saddle, accessible from behind.

Floyd Rose and locking tremolo systems

Floyd Rose and similar locking tremolo systems have saddles locked in place with an Allen key bolt. To adjust intonation:

1. Loosen the locking screw on the saddle
2. Use a hex key (Allen wrench) to move the saddle forward or back in its channel
3. Retighten the locking screw

The lock-down mechanism means saddles do not move under string tension once set, making Floyd Rose intonation very stable once set correctly.

Acoustic guitars

Acoustic guitars have a fixed nut and saddle — they cannot be adjusted fret by fret. The saddle (the white or bone piece at the bridge where the strings pass over) can be modified:

• Sharp intonation (fretted note sharper than harmonic): Carefully sand the front of the saddle to move the break point slightly back. This is irreversible and should be done carefully, in small increments.
• Flat intonation (fretted note flatter than harmonic): More difficult — the saddle would need to be replaced with one properly fitted to the correct position.

For acoustic guitars, a luthier (guitar technician) can adjust the saddle more precisely than most home players can. If your acoustic guitar has significant intonation problems, take it to a professional.

Step 6: Retune and Recheck

After each saddle adjustment:

1. Tune the open string back to pitch
2. Check the 12th fret harmonic (still correct)
3. Check the 12th fret fretted note

Repeat until the fretted note and harmonic match. Then move to the next string.

Work through all six strings in any order (many players go E6, A5, D4, G3, B2, E1).

Additional Check: The 5th or 7th Fret

Once the 12th fret is correct, play a few notes at the 5th and 7th frets. These should also be close to in-tune. If the 12th fret is correct but 5th and 7th feel off, there may be a nut issue (the nut slots may be cut incorrectly, causing sharp readings at the 1st and 2nd frets that compound at mid-fret positions).

Why Does Intonation Go Out?

Intonation changes over time because:

• String gauge change: Heavier strings have more tension and require the saddle to be repositioned
• String brand change: Different strings have different tension characteristics
• Temperature and humidity: Wood changes with environmental conditions, affecting neck relief and nut slot depth
• Age: Nuts and saddles wear over time

If you change string gauges, expect to reset intonation.

What If Adjusting the Saddle Doesn't Fix It?

If you've moved the saddle to the extreme of its travel and still cannot get accurate intonation:

• Too sharp even at maximum back position: The nut may be cut too low, or the saddle slot may be positioned incorrectly. Professional setup required.
• Too flat even at maximum forward position: The nut may be cut too deep, causing the open strings to be slightly flat. Professional setup required.
• String buzzing after adjustment: You may have changed the string height (action) as well as intonation. Check your saddle height after adjusting intonation length.

If in doubt, take the guitar to a guitar tech. A full setup including intonation, action, and truss rod adjustment typically costs £40–£80 and transforms the playability of a guitar.

How Often Should You Check Intonation?

• Every time you change string gauge
• Every time you change string brand (particularly if going from one manufacturer to another)
• Every few months as part of a general maintenance routine
• After any significant temperature change (transporting a guitar from cold to warm, or vice versa)

Summary

Frequently Asked Questions

What is guitar intonation? The accuracy of pitch across the entire fretboard. A guitar with good intonation plays in tune at every fret. Poor intonation means the guitar drifts sharp or flat as you move up the neck.

How do you check guitar intonation? Compare the 12th fret harmonic to the 12th fret fretted note using a tuner. They should match. If the fretted note is sharp, the saddle needs to go back. If it is flat, the saddle needs to go forward.

Why does my guitar go sharp up the neck? Usually an intonation problem (saddle too far forward, making the string too short). Less commonly, it can be a nut issue (slots cut too low) or a problem with neck relief.

Can you set intonation on an acoustic guitar? To a limited degree — a guitar tech can modify the saddle position. Acoustic guitars do not have individually adjustable saddles, so this requires physical modification.

How much does it cost to have intonation set professionally? A full guitar setup (which includes intonation, action, truss rod, and nut check) costs approximately £40–£80 at a guitar technician. Worth doing at least once per year.