Online Instrument Tuner

A tuner listens to a note and tells you how far from correct it is. The old way was a pitch pipe or a tuning fork; today a phone microphone and a bit of mathematics do the same. This tuner works in the browser: choose an instrument, play one string at a time, and a needle shows whether the pitch is flat, sharp or in tune.

How the pitch is found

A musical note is a repeating wave. The tuner takes a block of audio and looks for the shortest time after which the wave repeats itself, with a method called YIN, a refinement of autocorrelation. That period gives the frequency. The frequency is then compared with the nearest note of equal temperament, using the reference A4 you set, and the gap is expressed in cents. A cent is a hundredth of a semitone, so +10 cents is a tenth of the way to the next note. Smoothing over the last five readings stops the needle from shaking.

A worked example

Press Sample to see the display without a microphone: the note A2 with -12 cents and 109.2 Hz, flat. With a real A string played on a guitar tuned correctly, the reading is A2 at +0 cents and 110.0 Hz; the needle is at the centre and the display says In tune. Within plus or minus 5 cents the page treats the note as in tune. A slightly low string shows a message to tighten it, and a high string to loosen it.

Instruments and tunings

Chromatic mode names whichever note you play. The other modes know the open strings: guitar E2 A2 D3 G3 B3 E4; drop D with the low string at D2; four-string bass E1 A1 D2 G2; ukulele G4 C4 E4 A4; violin G3 D4 A4 E5; viola C3 G3 D4 A4; cello C2 G2 D3 A3; and mandolin G3 D4 A4 E5. The tuner picks the string nearest to what it hears, and buttons play a reference note for each string so you can match by ear. A reference of 440 Hz is standard, though some orchestras use 442 Hz, and early music is often at 415 Hz.

Getting a good reading

Play one string at a time, and let it ring. Strike gently, because the pitch of a string is briefly sharp just after a hard pluck. Stay away from noisy fans, a television or other instruments. Tune upwards to the note, approaching from below, which helps strings to hold. Check the low strings again after tuning the others, because tension changes in the neck. The page keeps the last reading for 1.5 seconds after the sound fades so you can read it.

Edge cases

The detector searches from 25 Hz to 1,700 Hz, which covers the open strings of every listed instrument, down to the 41 Hz low E of a bass. Notes outside that range, such as a high whistle or a beep above about 1.7 kHz, are not read. Chords confuse a single-pitch detector, so play single notes. On a weak low string the detector can occasionally lock onto an octave above or below; a stronger, gentler pluck usually fixes it.

Limits

This is a phone-grade tuner: accurate to a few cents in quiet conditions, which is enough for strings by ear but not for setting intonation on a studio instrument. It needs microphone permission, and the audio is analysed on your device without being stored or sent.

Related tools

• Tone Generator plays a steady reference tone.
• Note Frequency Chart gives the target frequency for any note you tune to.
• Ukulele Chord Finder shows chords once the instrument is in tune.
• Vocal Range Test uses the same pitch detector for your voice.