Online Guitar Tuner

How to get an accurate reading

Play one string, cleanly, and let it ring. A tuner works out the period of a repeating waveform, so two strings at once gives it two answers and it will flicker between them. Mute everything else with your palm.

Pick softly. A hard pluck sharpens the note for the first half second while the string is stretched, which is real physics rather than a tuner fault. Let the attack pass and read the steady part.

Tune up to the note, never down to it. Going up puts the string under tension against the tuning post and it stays. Arriving from above leaves slack in the post and the string drifts flat within minutes. If you overshoot, drop well below and come back up.

Go round twice. Tightening one string raises the tension on the neck and pulls every other string slightly flat. On a guitar with a floating tremolo it takes three or four passes to settle.

Cents, and how close is close enough

A cent is one hundredth of a semitone. The meter above shows how far the note sits from where it should be, and anything inside the green band, five cents either way, is closer than most people can hear on a single note.

Where it starts to matter is in chords, because errors add up. Two strings four cents apart in opposite directions are eight cents apart from each other, and that is audible as a slow beating in a held chord. If a chord sounds restless while every string reads in tune individually, that is what you are hearing.

One honest limitation nobody mentions: a guitar cannot be perfectly in tune with itself. Frets are laid out in equal temperament, so every chord shape is a small compromise. This is why an open G can sound sweet and a barre F sound slightly sour on the same perfectly tuned instrument, and why some players deliberately tune the B string a couple of cents flat.

When the tuner is not the problem

If a string reads in tune open but sharp at the twelfth fret, the intonation is out and no amount of tuning fixes it; the saddle needs moving back. If the first few frets play sharp while the rest of the neck is fine, the nut slots are cut too high. And if a string will not hold tune for five minutes, the usual culprits are a string that was never stretched in after fitting, a binding nut slot, or a tuning post that was wound the wrong way.