Guitar Tuner
Tune a guitar by ear-free measurement — cents, not colours, and no app.
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not listening
6th — E
82.4 Hz
5th — A
110.0 Hz
4th — D
146.8 Hz
3rd — G
196.0 Hz
2nd — B
246.9 Hz
1st — e
329.6 Hz
How this test works
The microphone stream is analysed by autocorrelation: the tool finds the period at which the whole waveform repeats, which is the fundamental frequency even when it is not the loudest thing in the sound. That matters on a guitar, because a plucked low E often has a stronger second harmonic than fundamental, and a detector that simply takes the loudest frequency reports the wrong string. The reading is converted to the nearest note and the deviation shown in cents — hundredths of a semitone — because the ear works in ratios and 3 Hz means something completely different on a low E than on a top E.
What the results mean
- Cents
- A hundredth of a semitone. Within ±5 counts as in tune; that is roughly what a trained ear resolves on a sustained note and better than a guitar holds through a chord.
- Clarity
- How periodic the signal is. A low figure means the microphone is hearing noise or several notes at once rather than one string.
- Nearest string
- Which of the six standard strings the detected note is closest to — useful when a string is far enough out to be ambiguous.
- Microphone processing
- A warning that the browser would not switch off noise suppression or automatic gain, both of which distort a sustained tone.
Common problems and fixes
- The note jumps around
- Play one string at a time and let it ring. A chord gives the detector several fundamentals and it will pick between them.
- It shows a note an octave out
- Usually a very quiet fundamental — common on a low E through a phone microphone. Play a little harder and closer.
- The reading drifts as the note decays
- Normal. A string goes slightly sharp as it is plucked and settles as it decays; take the reading a second after the attack.
- It never detects anything
- Check the microphone permission and that the right input is selected. The clarity figure staying at zero with a note playing means the stream is silent, not that the tuner is confused.
Frequently asked questions
How accurate is an online guitar tuner?
Good enough to tune with, in a quiet room. The limit is the microphone and the room rather than the arithmetic: the detector interpolates between samples for sub-cent resolution, and what degrades it is background noise, a rattling phone speaker, or several strings ringing at once. Play one string at a time and it will be within a few cents, which is inside what anyone can hear.
Should I tune up to the note or down to it?
Up. A string tuned down to pitch leaves slack in the winding and at the nut, which settles out over the next few minutes and pulls the note sharp again. Coming up to the note puts the tension the right way round. If you overshoot, go below and come back up rather than easing down.
Is my microphone audio recorded?
No. The stream is analysed frame by frame in the page and nothing is retained — there is no recording, no upload and no server involved at any point.