Free Online Guitar Tuner
Tune any 6-string guitar in seven different tunings. Enable your microphone for live pitch detection, or use the reference tones below to tune by ear. No download, no sign-up, runs in your browser.
Reference tones — tune by ear
Tap any string label below to hear the target pitch. Match your guitar string to it by ear. No microphone needed.
Reference pitches are generated at A=440 Hz concert pitch. The human ear is surprisingly good at hearing two notes drift apart — listen for the beating.
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About this tuner
Standard tuning is EADGBE at A=440 Hz concert pitch. The tuner above supports seven tunings — standard plus six common alternates — and works on any 6-string guitar. The active microphone tuner uses the YIN pitch-detection method — a difference-function refinement of autocorrelation that resists octave errors — together with a stable-pitch lock and a median filter to keep the display steady through the note's decay. The reference-tone tuner generates synthesised target pitches you can match by ear. Both are free, run in your browser, and require no sign-up.
How a digital guitar tuner actually works
When you pluck a guitar string, it vibrates at a fundamental frequency plus a series of weaker harmonics (overtones) at integer multiples of that fundamental. The tuner's job is to find the fundamental and tell you which note it is.
This tuner uses the YIN algorithm (de Cheveigné & Kawahara, 2002), a time-domain method built on the difference function — a close cousin of autocorrelation. Every animation frame the browser hands the tuner a snapshot of about 4,000 samples — roughly 93 milliseconds — of audio from your microphone. Instead of asking where the waveform best correlates with a shifted copy of itself, YIN asks where it best matches (smallest squared difference), then normalises that with a cumulative mean and takes the first dip below a fixed threshold rather than the global best. That "first dip, not best dip" rule is the whole trick: it stops the detector sliding onto a harmonic. Divide the sample rate by the resulting period and you have the frequency in Hz; take the base-2 logarithm of (frequency ÷ 440 Hz), multiply by 12, add 69, and you have the MIDI note number, whose fractional part times 100 is the cents reading.
Octave errors are the classic failure of cheaper detectors. A sharply-plucked low E string can have a louder second harmonic than fundamental, which trips up the most obvious approach — picking the strongest peak in an FFT — and makes those tuners read the note an octave too high. A plain peak-picking autocorrelation has the mirror problem: it can lock onto twice the true period and read an octave too low. YIN's first-dip-below-threshold rule, plus an octave-snap guard that folds any stray half- or double-frequency reading back onto the established note, keeps the displayed octave correct from the first clean frame.
On top of detection sit two stabilisers. A median filter over the last several frames means a single bad reading cannot move the display. And a stable-pitch lock handles inharmonicity — a real physical effect where a stiff steel string's perceived fundamental drifts 5–30 cents as it decays, worst on the plain (unwound) D, G, B and high-E strings. Once the tuner sees four or more samples within 10 cents of each other it locks onto that pitch and holds it steady, ignoring octave glitches and releasing only when you make a sustained, deliberate adjustment. The result is a reading taken from the body of the note, not the noisy decay tail.
What "cents" means — and why every honest tuner shows them
A cent is a logarithmic unit of musical pitch. One semitone — the distance from E to F, or B to C — is exactly 100 cents. The interval was proposed by Alexander Ellis in 1885 in his appendix to Hermann von Helmholtz's On the Sensations of Tone, precisely because musicians needed a way to talk about pitches between the named notes.
A reading of +12 cents means the played note is 12% of a semitone sharp — higher than the target. -8 cents means 8% of a semitone flat. Professional studio musicians generally aim for ±3 cents on each note. Most guitarists are satisfied at ±5 cents; the human ear can usually hear something starting to sound "off" beyond about ±15 cents, depending on the timbre and how long the note rings.
The reason the cents display matters — and the reason cheap clip-on tuners that only show "in tune / sharp / flat" arrows are useless for serious work — is that the size of "in tune" is genuinely tiny. A 5-cent error at the open low E is about 0.24 Hz: the difference between 82.41 Hz and 82.65 Hz. You cannot reliably tune to that resolution by reading a green/red light. You can if you can see the actual cents number.
The 7 tunings and when to use them
| Tuning | Notes | Used by / for |
|---|---|---|
| Standard | EADGBE | The default for most music — rock, pop, blues, country, jazz. Tuned in perfect fourths except between strings 3 and 2, which is a major third. The most common tuning by an enormous margin. |
| Drop D | DADGBE | Heavier rock, metal, and folk fingerpicking. The low E drops a whole step to D — every other string stays in standard tuning. The low D produces a one-finger power chord on the bottom three strings. |
| Drop C | CGCFAD | Modern metal — everything down one whole step from Drop D. The low string drops to C2 (about 65 Hz), giving the heaviest tonal range without switching to a baritone guitar. |
| Half-step Down | Eb-Ab-Db-Gb-Bb-Eb | Hendrix, Stevie Ray Vaughan, Guns N' Roses. Every string drops a half step (one semitone). Easier on the voice for tenor singers and easier on the fingers for string bending — gauge 0.10 strings at Eb feel like 0.09 strings at E. |
| Open G | DGDGBD | Keith Richards' signature Rolling Stones tuning, most slide blues, country lap-style. Strummed open, the strings sound a G major chord — major-key drone runs and slide work are immediate. |
| Open D | DADF#AD | Joni Mitchell, slide guitar, country-blues fingerpicking. Open strings strum a D major chord. The low D combined with a high octave-D drone makes the guitar feel like a much bigger instrument. |
| DADGAD | DADGAD | Pierre Bensusan, Celtic and modal music, modern fingerstyle. A modal tuning — not major, not minor. The open chord is suspended, producing ambiguity that fits Celtic and meditative repertoire. |
Highlighted row is the standard. Beyond these seven, dozens of less common tunings exist — Open C, Open E, New Standard Tuning, all-fourths tuning, and a great many personal tunings used by individual songwriters (Joni Mitchell alone has been credited with over 50). For 99% of working guitarists the seven above cover everything.
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Tips for getting an actually-in-tune guitar
Always tune up to pitch, not down. Guitar machine heads have a small amount of mechanical backlash. Tuning up under string tension takes that slack out and produces a stable reading. If a string is sharp, tune it deliberately flat (below pitch) and then come up to pitch from below. Tune down to pitch and the string will drift sharp again as you play.
Tune in the order you'll play. If you're tuning before a recording or a gig, do the strings in the order you usually pick them. Each tuning interaction pulls slightly on the rest of the neck; getting all six "in tune" simultaneously requires going back and rechecking one or two more times.
Pluck gently for the tuner; harder for the music. A heavy pluck on a steel string momentarily bends sharp by 5–10 cents before settling back to true pitch. Tune with a light pluck — what your guitar will read on the tuner is what it will sound like a second after a normal-strength pick attack.
If your tuner shows every string in tune but the guitar still sounds wrong, the problem is probably intonation, not tuning. Intonation is whether the fretted notes stay in tune at the 12th fret as well as they do at the open string. Bad intonation is a setup problem (saddle position, neck relief, fret wear) — no tuner can fix it. If your tuned-perfectly-open guitar plays sharp at the 12th fret, take it to a luthier for a setup.
Frequently asked
+Is this guitar tuner free?
Yes. The tuner runs entirely in your web browser. No download, no sign-up, no paid version, no usage limit.
+Does it work on my phone?
Yes — both the active microphone tuner and the reference-tone tuner work on iOS Safari, Chrome on Android, and any modern mobile browser. On a phone, hold the device about 6–12 inches from the guitar for the cleanest signal.
+Why does the needle hold its position after the note fades?
That is the stable-pitch lock working as intended. Once the tuner has four or more steady pitch samples it locks onto the body-of-note pitch and shows a HELD badge, so you can read the result after the string has decayed instead of watching the number scatter into the noise. Pluck again and it re-reads live.
+Why does the Enable Microphone button do nothing on my Android phone?
Most likely the site needs to be on HTTPS (a padlock should be visible in the address bar — mic access is blocked on plain HTTP), or microphone access for this site was previously denied. Tap the lock icon or the three dots in the address bar, then Site settings, then allow microphone, and reload the page. If you are using Motorola's bundled browser or Samsung Internet and still have trouble, try installing Chrome or Firefox from the Play Store — both have reliable mic permission flows.
+Is my audio uploaded or recorded?
No. Microphone audio is processed entirely in your browser using the Web Audio API. The audio data never leaves your device — not sent to a server, not stored, not used for anything other than displaying the detected pitch in real time. Closing this page ends the audio session.
+What does A=440 Hz mean?
A=440 Hz is "concert pitch" — the standard tuning reference used worldwide. It means the open A above middle C (called A4 by musicians, MIDI note 69) is set to 440.00 Hz. Every other note is derived from this reference. Some musicians prefer A=432 Hz (a controversial alternative); some baroque ensembles use A=415 Hz; almost everyone else uses A=440.
+Why does my tuner show different readings each pluck?
A vibrating string is a slightly chaotic system. Each pluck attack contains transient pitch wobble in the first 100–200 milliseconds before the steady tone settles in. This tuner uses a median filter and a stable-pitch lock to capture the cleanest portion of the note and ignore the wobble; if readings are still wildly unstable, check for background noise (a nearby fan, fluorescent buzz, traffic) and try plucking more gently.
+I tuned my open strings but the chords still sound out of tune.
That's an intonation problem, not a tuning problem. The 12th-fret harmonic and the 12th-fret fretted note should be the same pitch; if the fretted note is sharp, your saddle needs to be moved further back from the nut. This is a one-time setup adjustment that a guitar tech can do in 15 minutes.
Related guitar pages
Sources & technical references
- Alain de Cheveigné and Hideki Kawahara, "YIN, a fundamental frequency estimator for speech and music," Journal of the Acoustical Society of America 111(4), 2002 — the difference-function pitch detector used by this tuner.
- Alexander J. Ellis, "On the Musical Scales of Various Nations," Journal of the Society of Arts Vol. 33 (1885) — the original proposal of the cent as a unit of musical interval.
- Hermann von Helmholtz, On the Sensations of Tone as a Physiological Basis for the Theory of Music, 2nd English edition translated by Ellis (Longmans, Green and Co., 1885) — the standard 19th-century reference on the physics of musical pitch.
- Harvey Fletcher, E. Donnell Blackham and Richard Stratton, "Quality of Piano Tones," Journal of the Acoustical Society of America, 1962 — the foundational study of piano-string inharmonicity, with results that apply directly to steel guitar strings.
- Julius O. Smith III, Mathematics of the Discrete Fourier Transform (DFT) with Audio Applications (W3K Publishing, 2nd ed. 2007) — Stanford CCRMA reference on the FFT vs time-domain tradeoff for pitch detection.
- The International Organization for Standardization, ISO 16:1975 — the standard establishing A=440 Hz as concert pitch.
- MIDI Manufacturers Association, The Complete MIDI 1.0 Detailed Specification (1996, revised 2014) — the standard note-numbering scheme used throughout this tuner.
- The stable-pitch lock is an original adaptation: when 4+ consecutive pitch samples sit within 10 cents, lock the display to that value; release on a sustained 18-cent drift (a genuine adjustment) but ignore 1200-cent shifts (octave-harmonic detection errors). Combined with a median filter and an octave-snap guard, it keeps the display on the body-of-note pitch rather than chasing inharmonicity drift in the decay tail.
Tune up to pitch. Pluck gently. Check it twice. You're done.