Online Tuner

Hear a string and see its pitch on a needle

An online tuner listens to your instrument through the microphone of your phone or computer and shows, with a needle and a number, how far the sound is above or below the target note. Choose guitar, bass, ukulele, violin or viola, or cello, and it finds the string closest to what it hears. Choose ‘All notes’ and it finds the nearest of the 12 semitones instead, so sounds without strings, such as singing or a wind instrument, can be checked too.

When the needle enters the centre ‘in tune’ zone, its colour changes, and once the same string has stayed in tune for 0.5 seconds, that string gets a tuned mark on the string rail. The strobe band under the gauge drifts left when the sound is low and right when it is high, and slows down as you approach the target, so even a difference of a few cents is easy to see. The trace line at the bottom draws the pitch of the last 10 seconds, showing how the sound approaches the target as you tighten the string and how much it wavers. The sound is analyzed only on this device and is never recorded or sent to a server.

When you need a tuner

Strings keep moving after you have tuned them. The guitar-parts company StewMac explains that new strings stretch and settle while you play, so the pitch keeps drifting flat in the meantime, and that temperature, humidity and hard playing also change the tuning. So it is worth checking the tuning every time you start practising, and in cases like these.

• After fitting new strings: the strings stretch and the pitch keeps falling, so tune, play for a few minutes, and tune again, a few times over.
• When playing with other instruments: everyone has to tune to the same reference pitch or the harmony will clash. If the piano or ensemble you play with uses 442 Hz, change the reference A4 box to 442.
• When changing tuning for a song: when you move to a tuning that changes some strings, such as Drop D, half step down, DADGAD or Open G, you can check the new target note of each string right away.
• When it is hard to tune by ear: beginners often cannot hear a difference of a few cents. The needle and the strobe band make that difference visible.
• When you cannot use the microphone: select a string and tap ‘Play’ to hear its target note, then tune by ear against that reference.

How to use it

1. Choose the instrument and the tuning. Guitar standard tuning (E A D G B E) is selected at first. If you play with a piano or an ensemble, set the reference A4 to match theirs.
2. Tap ‘Start mic and tune’. Allow microphone access when the browser asks, and put your phone or laptop close to the body of the instrument.
3. Pluck one string at a time and let it ring. Lightly muting the other strings with your hand keeps them from ringing along and makes the reading more stable.
4. Turn the tuning peg while watching the needle. If the needle is on the left (flat), tighten the string; if it is on the right (sharp), loosen it a little and then tune up to the note from below. The string is in tune when the number is near 0 and the needle changes colour.
5. When every string has a tuned mark, check once more. Pluck them again in order from the first string. For a string that is far off, tap it on the string rail to lock it, so it is not misread as a neighbouring string.

Standard tunings and frequencies by instrument

The frequencies below are equal-temperament values for A4 = 440 Hz, listed from the thickest string (the highest string number) to the thinnest. On a guitar, the highest string is string 1 and the lowest is string 6.

Standard ukulele tuning is ‘re-entrant’: string 4 (G4) is higher than string 3 (C4). This tuner finds the target note whatever the string order, so choose standard (high G) or low G to match the string you use, and you will not tune string 4 an octave off. The low B0 of a 5-string bass is about 31 Hz, which reaches a phone microphone only weakly, but its overtones repeat at the same period, so the pitch can still be read.

Guitar tunings

When you change the tuning box, the target notes and frequencies on the string rail change at once. If several strings change, first bring the ones that move most roughly to pitch, and after you have changed all of them, check from the first string once more.

Reading the screen: cents and the verdict

The cent is a unit for the difference in pitch between two notes: an octave is divided into 1,200 cents and an equal-tempered semitone into 100. Alexander J. Ellis introduced this system formally in an 1885 paper. The formula is cents = 1200 × log₂(heard frequency ÷ target frequency), which is negative when the sound is below the target and positive when it is above.

This tuner calls a note ‘in tune’ when the rounded cents shown on screen are between −3 and +3. That is narrower than the roughly 5–6 cents that is said to be the smallest pitch difference people can tell apart. When the sound is more than 50 cents (half a semitone) off, the needle stays at the end and a number tells you how many semitones below or above the target it is.

The last row is the case where string 5 (A2) is locked and the sound of G2 comes in. The frequency line also shows the semitone nearest to the sound as the ‘heard’ note, so with a string locked you can still tell which string was sounded. On the trace, check whether the line stays inside the centre band (±3 cents). A line that waves evenly up and down means the note is wavering, like vibrato.

Changing the reference pitch A4

The International Organization for Standardization (ISO) adopted 440 Hz for the A above middle C (A4) in 1955 and confirmed it again as ISO 16 in 1975. In practice, the reference differs a little from place to place. In 1964, 19 of 31 major American orchestras used 440 Hz and the rest used 441–442 Hz, and the Berlin Philharmonic is known to use 443 Hz. Baroque ensembles sometimes use 415 Hz.

When you change the reference, every string’s target frequency moves by the same ratio. Target frequency = A4 × 2^{(n − 69) ÷ 12}, where n is the MIDI number of the note (A4 = 69, middle C = C4 = 60). Raising A4 by 1 Hz raises every note by about 3.9 cents.

Tips for tuning more accurately

• Tune up from below. StewMac advises tightening from slightly below the target and, if you overshoot, going back down and coming up again. A string tuned down from above can sag a little afterwards because of slack in the tuning gear or the string. That is why this tuner says ‘loosen a little, then tune up from below’ when the note is high.
• Sound one string at a time. When several strings ring together, the tuner may read just one of the notes, or a note nobody played because the two sounds overlap into a longer common period. Lightly mute the strings you are not tuning with your palm.
• Watch while the note sustains, not right after the pluck. Thick strings have strong inharmonicity, meaning their overtones sit slightly above exact whole-number multiples, so the value read at the instant of the pluck can differ a little from the value as the sound dies away. This tuner shows the median of the last 0.35 seconds, so go by the number while the note is sustaining.
• On a violin, use the pegs and the fine tuners separately. A violin is tuned with the pegs at the scroll or with the fine-tuner screws on the tailpiece, and some instruments have no fine tuners. Bring a far-off string close with the peg, then set the last few cents with the fine tuner.
• Lock a badly slack string. Automatic search picks the nearest string, so a string that is several semitones off can be read as its neighbour. Tap the string you want on the string rail to judge only against that string, and tap again to return to automatic.
• Stay in a quiet place with the mic close. Air conditioning, voices or music make the period of the sound unclear, and the needle stops.

How the pitch is measured

More than 30 times a second, this tuner reads the latest 0.085 seconds of microphone sound (4,096 samples at 48 kHz) and looks for the fundamental frequency. The method is the normalised square difference function (NSDF) proposed by McLeod and Wyvill. If you shift the sound by τ and compare it with the original, n(τ) = 2r(τ) ÷ m(τ) has a peak close to 1 when the shift equals one period of the sound. Of the several peaks, the first one that exceeds 0.9 times the highest value is taken as one period, and parabolic interpolation gives its position between samples. The tuner then measures a distant multiple of the same period again and divides by the multiple to reduce the error further.

Finding the fundamental frequency from autocorrelation is widely used for speech and music, and YIN, published by de Cheveigné and Kawahara, belongs to the same family of methods. When an instrument is selected, notes more than a perfect fifth below its lowest string are not judged, and if there are several period candidates, the one within 50 cents of a string in that tuning is tried first. This keeps the longer common period of two ringing strings from being read as the wrong string. The thresholds used for the verdict are below.

Common mistakes

• Mixing up string 6 and string 1: both are E, but two octaves apart (E2 82.41 Hz, E4 329.63 Hz). Check the small number next to the note name (the octave) as well.
• Tuning a half-step-down song to standard: if the song you play is a half step down, every string will be off by a semitone. Choose ‘Half step down’ in the tuning box and the targets become E♭ A♭ D♭ G♭ B♭ E♭.
• Tuning ukulele string 4 an octave low: a high G string tuned to G3 goes too slack. Choose standard (high G) and the string 4 target is G4 (392.00 Hz).
• Playing with an instrument on a different reference pitch: if you tune alone to 440 Hz and play with a piano at 442 Hz, everything sounds about 8 cents flat. Set the reference pitch before you play together.
• Judging a Drop D string against standard tuning: with the tuning box on standard, string 6 lowered to D2 reads ‘2.0 semitones below’ E2. If the song is in Drop D, choose ‘Drop D’ in the tuning box.

Limitations

• It reads one note at a time. For a chord with several strings sounded together, it gives no verdict, or reads one of the notes or a note that was not played.
• Bluetooth earphone microphones and video-call devices process the sound inside the device, which can weaken low notes. This tuner asks the browser to turn off noise suppression and automatic gain control, but some devices may not apply that.
• A phone may stop the microphone when the screen turns off or you switch to another app. The tuner asks to keep the screen awake while listening, but some browsers do not support that.
• The detection range is 25–2,200 Hz. Notes outside it are not read, and even inside it low notes may reach the microphone weakly, depending on the microphone.
• Target notes are equal-temperament values. Other temperaments, such as just intonation, are not taken into account.

Reference date The sources were checked on 2026-10-27.

Sources

• 01Wikipedia: Guitar tuningsStandard tuning E2–A2–D3–G3–B3–E4, the highest string is string 1 and the lowest is string 6, Drop D lowers only string 6 by a whole step, Open G is D–G–D–G–B–D, E♭ tuning with every string down a half step
• 02Wikipedia: DADGADFrom the lowest string: D2 A2 D3 G3 A3 D4
• 03Wikipedia: Bass guitar4-string bass E1–A1–D2–G2, the 5-string adds a low B string
• 04Wikipedia: UkuleleStandard G4–C4–E4–A4 (high G, re-entrant), low G is G3–C4–E4–A4, baritone is D3–G3–B3–E4
• 05Wikipedia: Violin · Viola · CelloViolin G3 D4 A4 E5, tuned with the pegs or with fine tuners on the tailpiece (fine tuners are optional), viola C3 G3 D4 A4, cello C2 G2 D3 A3
• 06Wikipedia: Cent (music)1,200 cents to the octave, 100 cents to an equal-tempered semitone, formally introduced by Ellis (1885), discernible pitch difference about 5–6 cents
• 07Wikipedia: Concert pitchISO adopted A440 in 1955 and reaffirmed it as ISO 16 in 1975, in 1964 19 of 31 major American orchestras used 440 Hz (the rest 441–442 Hz), Berlin Philharmonic 443 Hz, Baroque ensembles 415 Hz
• 08StewMac: 5 Reasons Your Guitar Won’t Stay In TuneNew strings go flat until they settle, temperature, humidity and playing habits change the tuning, tune up from slightly below the target (slack in the gear or the string)
• 09McLeod and Wyvill, A Smarter Way to Find Pitch (University of Otago, web archive PDF)Normalised square difference function n′(τ) = 2r′(τ) ÷ m′(τ), the first key maximum above the highest peak × k, k usually 0.8–1.0, parabolic interpolation
• 10de Cheveigné and Kawahara (2002), YIN, a fundamental frequency estimator for speech and music, JASA 111(4)Fundamental frequency estimation for speech and music, built on the well-known autocorrelation method with several modifications that prevent errors
• 11Wikipedia: InharmonicityThe vibration of a stiff string departs from exact whole-number overtones, and the departure is larger on thick low strings
• 12MDN: AnalyserNode.getFloatTimeDomainData()A Web Audio method that copies the latest samples of the incoming sound into an array

Frequently asked questions

Tools to use with it