You can tune perfectly and still sound wrong. If your open strings read in tune but chords higher up the neck sound sour, you are dealing with intonation.
This guide explains intonation in plain English, shows a quick check you can do with an online tuner, and helps you decide whether you can fix it yourself or you should hand it to a tech.
Quick CTA:
- Tune first: Guitar standard tuning
- Troubleshooting guide: Why your guitar won't stay in tune
What intonation means (plain English)
Intonation means your guitar plays in tune up and down the neck, not only on open strings.
When intonation is off, two statements can be true at the same time:
- Your tuner says the open string is correct.
- Your chord at the 5th or 12th fret sounds wrong.
Intonation is mostly about string length and setup. If the string length is not set correctly for your guitar, notes go sharp or flat as you fret higher.
Signs you have an intonation problem
Look for these patterns:
- Open strings sound fine, but barre chords sound off.
- A chord sounds ok in one position and wrong in another.
- You tune, play one song, and feel like you are chasing pitch all night.
Before you blame intonation, check two basics:
- Are your strings old? Old strings can sound sour no matter what.
- Are you pressing too hard? Heavy fretting pressure can pull notes sharp.
Quick intonation check with an online tuner
This check works best with:
- fresh-ish strings
- a quiet room
- a steady picking attack
Open the tuner:
Step 1: Tune the open string
Tune one string perfectly open. Start with the low E and work across.
Step 2: Compare the 12th-fret harmonic to the 12th-fret fretted note
For that same string:
- Play the 12th-fret harmonic (touch the string lightly over the 12th fret, then pluck).
- Check the tuner reading.
- Now fret the note at the 12th fret normally and pluck.
- Check the tuner reading again.
What you want:
- harmonic and fretted notes both center on the same pitch
What it means if they do not match:
- Fretted note is sharp: the string length is too short.
- Fretted note is flat: the string length is too long.
Repeat for each string.
Tip: use normal playing pressure. If you press too hard, you can make the fretted note look sharp even when the setup is fine.
What to do if intonation is off
The right fix depends on your instrument.
Electric guitars (adjustable saddles)
Most electric guitars have saddles you can move.
General rule:
- Fretted 12th note sharp: lengthen the string (saddle back).
- Fretted 12th note flat: shorten the string (saddle forward).
If you are comfortable with basic setup work, make small moves and retune after every adjustment. If you are not comfortable, a tech can do this quickly, and it is worth it.
Acoustic guitars (fixed saddles)
Most acoustics do not have adjustable saddles. Intonation fixes usually involve:
- saddle work
- nut work
- checking neck relief and action
Those are "take it to a tech" tasks for most players.
What affects intonation (so it does not surprise you later)
String gauge changes
If you change string gauges, intonation can change. Heavier strings often need saddle adjustments.
Action and neck relief
High action can pull notes sharp because you push the string farther to the fret. Neck relief changes can shift intonation too.
Tuning changes
Drop tunings and down-tunings can expose intonation issues, especially if tension gets loose.
If you play Drop D and it sounds muddy or out of tune, intonation is one possible cause:
FAQs: guitar intonation
Why do open strings tune fine but chords sound wrong?
Because intonation deals with fretted notes. Open strings only tell you one pitch per string.
Should I check intonation with old strings?
No. Old strings can be unstable and give misleading readings. If you cannot remember when you changed strings, start there.
Can I fix intonation without tools?
You can diagnose it without tools. Fixing it on electric guitars usually means moving saddles, which needs tools. On acoustic guitars, intonation work usually needs a tech.
Does intonation matter if I only play open chords?
Less, but it still matters. If you use a capo, play higher chords, or record layered parts, intonation becomes obvious fast.
Next step: run the 12th-fret check and decide your move
Start with a careful tune, then compare harmonic vs fretted at the 12th fret:
If tuning drifts constantly even after you address intonation, work through this checklist: