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Guitar Tuner

Tune your guitar, bass or ukulele with your microphone, or any instrument in chromatic mode.

Maintained by BrowserTools · Last updated 2026-09-29

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This tuner listens to your instrument through the microphone of your phone, tablet or computer and tells you whether each string is flat, sharp or in tune. Press Start, allow the microphone and pluck a string: the tuner recognises which string you are playing, shows its name, and moves the needle to show how far off you are in cents (hundredths of a semitone). When the needle sits in the green zone, within 5 cents of the target, the display turns green and the string is in tune. The frequency you are actually producing is shown underneath, which helps when a string is so far off that it sounds like a different note.

Frequently asked questions

How do I tune my guitar with this tuner?
Press Start and allow the microphone. Pluck the low E string and let it ring. The big letter shows the string the tuner thinks you are tuning, and the needle shows whether it is flat (left) or sharp (right). Turn the peg slowly until the needle stays in the green zone, then move on to the next string. When all six strings are green, check them once more, because tightening one string slightly changes the tension on the neck.
What do the cents on the meter mean?
A cent is one hundredth of a semitone, so the meter from -50 to +50 cents covers the distance to the next note on either side. Most people cannot hear a difference of less than about 5 cents, which is why the green zone is 5 cents wide in each direction. Past 50 cents the needle stays at the edge and the text tells you the note is much too low or much too high.
Why does the tuner show the wrong string?
In automatic mode the tuner picks the string whose note is closest to what it hears. A brand new string or a guitar that is far out of tune can be closer to a neighbouring string's note than to its own. Tap the string you want to tune to lock the tuner onto it, tune until the needle is green, then switch automatic detection back on.
Can I tune a bass, ukulele or other instrument?
Yes. Choose 4-string or 5-string bass, or ukulele (G C E A), from the instrument list. For anything else, such as violin, cello, mandolin, banjo, wind instruments or a singing voice, choose Chromatic: the tuner then shows the nearest note of the chromatic scale and how many cents you are away from it.
What is the A4 reference and should I change it?
A4 is the A above middle C, and it defines the pitch of every other note. The international standard is 440 Hz, and you should leave it there unless you need to match something else. Some orchestras tune to 441 to 443 Hz, some baroque ensembles to lower pitches, and if you play along with a recording or a piano that is slightly off, matching its A keeps you together.
Is my microphone audio recorded or sent anywhere?
No. The sound goes from your microphone to the pitch detection code running on this page and is only used to measure the note. Nothing is recorded, saved or uploaded, and the microphone is released as soon as you press Stop or close the page.
The needle jumps around or nothing is detected. What can I do?
Move closer to the instrument and pluck one string at a time, muting the others with your hand if they ring along. Background noise, talking and fans make it harder to read the pitch. If nothing is detected at all, check that the browser is allowed to use the microphone and that the level bar at the bottom of the meter moves when you play. On a phone, make sure no other app is using the microphone.
Why is the low B of a 5-string bass slower to settle?
The lower a note, the longer each vibration takes: the low B vibrates only about 31 times per second. The tuner needs to hear at least two full vibrations for a reliable reading, so it uses a longer listening window for bass, which makes the display a little slower. Pluck firmly and let the note ring, and the reading will settle within a second.
How does the reference tone help?
The speaker button under each string plays that string's target note so you can tune by ear, which is useful when you want to train your hearing or the room is too noisy for the microphone. Play the tone, pluck the string, and adjust the peg until the slow wobble (the beating between the two sounds) disappears.

About Guitar Tuner

It covers the tunings people actually use. For guitar there is standard tuning (E A D G B E), Drop D, DADGAD, Open G and half step down (Eb Ab Db Gb Bb Eb); for bass, 4-string and 5-string with the low B; for ukulele, standard G C E A with the high G. Chromatic mode drops the presets and simply shows the nearest note for any sound, so you can use it for violin, cello, mandolin, wind instruments or your voice. Tap a string to lock the tuner onto it, which is useful for very slack new strings, and tap the speaker button under any string to hear a reference tone and tune by ear. The reference pitch A4 can be moved between 430 and 450 Hz for bands and orchestras that tune higher or lower than the usual 440 Hz.

For the best result, tune in a quiet room, hold the phone close to the sound hole or the amplifier, and pluck one string at a time, letting it ring. A firm pluck gives a strong start, but the reading settles as the note sustains, so watch the needle for a second or two rather than the first instant. Always tune up to the note: if a string is sharp, go below the target and come back up, because that seats the string in the tuning peg and it stays in tune longer. The sound is analysed live in your browser; nothing is recorded, stored or uploaded, and the microphone switches off as soon as you press Stop or leave the page.

Why 440 Hz, and how tuners learned to listen

For most of musical history there was no standard pitch. An A in Venice could be a semitone higher than one in Paris, and organs built in different towns could not play together. France fixed its diapason normal at 435 Hz in 1859, and an international conference in London in 1939 settled on 440 Hz, which the International Organization for Standardization confirmed as ISO 16 in 1975. Many orchestras still tune slightly higher, around 442 or 443 Hz, because a brighter pitch sounds more brilliant, and period instrument ensembles often tune to 415 Hz, about a semitone lower, to match the instruments of the baroque era.

Before electronics, musicians tuned with tuning forks, invented by the English trumpeter John Shore in 1711; he reportedly called his invention a pitch fork. The first electronic tuners were strobe tuners from the 1930s, where a spinning disc lit by a lamp flickering at the frequency of the note appears to stand still when the note is exactly right. Strobe tuners are still prized for their precision, and the scrolling band under this tuner's needle imitates them: it drifts left or right when a string is off and stops when it is in tune.

Software tuners like this one have to solve a surprisingly hard problem, because a plucked string is not a single frequency. It vibrates at its fundamental and at many overtones at the same time, and on low guitar and bass strings the second harmonic is often louder than the fundamental, which can fool a naive detector into reading the note an octave too high. This tuner uses the McLeod pitch method, published by Philip McLeod and Geoff Wyvill in 2005, which compares the sound with delayed copies of itself to find the repeating period, and is designed to pick the true period even when the overtones are strong.

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