How to use the online tuner
- Choose your instrument, or leave it on Any note (chromatic) to see the nearest note for whatever you play. Check the A4 reference, which is 440 Hz unless your group tunes differently.
- Press Start microphone and allow access when your browser asks. Play one note at a time and let it ring. The big letter is the note heard, the needle shows how far you are from it, and the message tells you whether to tune up or down.
- When the needle sits in the middle band and the message says In tune, move to the next string. With a named instrument, the nearest string is outlined among the reference buttons.
- To tune by ear, press a reference note button to hear a plain tone for a few seconds, and press it again to stop. Press Stop microphone when you are done.
Formula
Note number = 69 + 12 x log2(frequency / A4)
Frequency of a note = A4 x 2^((note number - 69) / 12)
Cents off = 1200 x log2(frequency heard / frequency of the nearest note)
This is equal temperament, where each semitone is the same ratio and there are 1200 cents in an octave. Note number 69 is A4 and 60 is middle C.
A guitar A string that is a little flat
With A4 at 440 Hz, the open A string of a guitar in standard tuning (A2) should sound at 110 Hz. Say the string sounds at 108 Hz. The ratio 108 / 110 gives 1200 x log2(0.9818), which is about 32 cents below the target, so the tuner shows A2, about 32 cents low, and says to tune up.
Tightening the string until it reads 110 Hz brings the offset to 0. If your group tunes to A4 = 432 Hz instead, the same string targets 108 Hz, so the first reading would have been in tune. Changing the reference moves every target at once.
How the pitch is found
The page reads short slices of sound from the microphone, about ten times a second, and compares each slice with a copy of itself shifted by different amounts. When the shift equals one period of the note, the two line up almost perfectly. The tool takes the first strong match, so a loud overtone is not mistaken for the note, and refines it to a fraction of a sample.
In the checks run for this tool, computer-made tones from about 40 Hz to 2 kHz were measured to within 0.02 cents, and a separate Fourier peak search agreed with the result. Real instruments are less clean than a test tone, and room noise, a weak microphone or a note that has just been plucked can all add error, so treat readings as accurate to a few cents at best. If the signal is too quiet or has no clear pitch, the tuner shows nothing rather than guessing.
Privacy and permissions
The microphone is requested only after you press Start microphone. Sound is analyzed in your browser tab as it arrives. It is not recorded, stored, played back or sent to any server, and the microphone is released as soon as you press Stop or leave the page. If access is blocked, the message explains how to allow it in your browser settings. If no microphone exists or another app is using it, the message says so, and the button works again afterward.
Echo cancellation, noise reduction and automatic gain are switched off so the signal reaches the tuner unchanged. If your device cannot start audio at all, the page says so instead of hanging.
Tips for a steady reading
Play a single string at a time and let it ring, because chords have no single pitch to read. Stay close to the microphone, keep other sounds quiet, and tune each string up to the note from slightly below, which keeps the string from slipping afterward. Very low notes, such as the lowest bass string, take a moment to settle because each cycle is long. To check intervals or write down a melody afterward, the metronome and the circle of fifths pair well with a tuner.
Assumptions and limits
- Notes are in equal temperament relative to the A4 reference you set, from 400 to 480 Hz. Other tuning systems, such as just intonation, are not shown.
- The instrument lists are common standard tunings, and players choose others. Use Any note (chromatic) for a tuning that is not listed.
- A reading within 5 cents of its target is called in tune. That limit is this tool's own choice and not a standard.
- The tuner finds one pitch at a time between about 30 Hz and 2.2 kHz. It does not separate several notes played together.
Frequently asked questions
Why does my browser ask for the microphone?
The tuner has to hear the note to measure it. It asks only after you press Start microphone, and nothing is recorded or sent anywhere.
Why does the tuner show a dash?
It shows a dash when the sound is too quiet or has no clear repeating pitch, such as noise or a chord. Play one note closer to the microphone.
Can I tune to 432 Hz or another reference?
Yes. Enter any value from 400 to 480 in the A4 reference box and every target note moves with it.
Why can I hear a tone but the tuner reads nothing?
A reference note is a separate feature that plays sound but does not feed the tuner by itself. The tuner only reacts to what the microphone picks up from the room.