How to Tune a Guitar

Standard tuning, and where those notes came from

A six-string guitar in standard tuning goes E A D G B E from the thickest string to the thinnest. Written properly with octave numbers that is E2, A2, D3, G3, B3 and E4, and at a reference pitch of A = 440 Hz those correspond to 82.41, 110.00, 146.83, 196.00, 246.94 and 329.63 hertz. The two outer strings are two octaves apart and share a letter name, which is why guitarists call the sixth and first strings "low E" and "high E" and why an open six-string strum sounds so resolved.

The spacing looks arbitrary until you count frets. Every gap is a perfect fourth — five semitones — except the one between the third and second strings, which is a major third of four semitones. That single irregularity is a deliberate compromise. Fourths all the way up would make scale fingerings perfectly symmetrical but would put common chord shapes out of reach of a human hand; the major third pulls the top two strings closer so that open chords, barre shapes and the standard pentatonic box all fall comfortably under four fingers. Nearly everything that feels awkward about guitar theory — why octave shapes shift a fret when they cross the G string, why the CAGED system looks the way it does — traces back to that one interval.

What "in tune" actually means: cents

Frequencies are multiplicative, not additive. Going up an octave doubles the frequency, so the distance from 110 Hz to 220 Hz and from 220 Hz to 440 Hz is the same musical interval despite being 110 Hz and 220 Hz apart. That makes raw hertz a terrible unit for describing how out of tune something is: being 3 Hz flat is a serious error on a low E and almost inaudible on a high E. So musicians use cents, a logarithmic unit where one semitone is 100 cents and an octave is 1200.

The conversion is one line of maths: cents = 1200 × log₂(measured ÷ target). A reading of +12 cents means you are just over a tenth of a semitone sharp regardless of which string you played, which is exactly the property you want from a tuning display. As a rough guide to what matters, a single sustained note played alone needs to be off by roughly 5 to 10 cents before most listeners notice. Two notes played together expose far smaller errors, because slightly mismatched frequencies produce audible beating — a slow throbbing in the volume at a rate equal to the difference between the two frequencies. Two A strings 1 Hz apart beat once per second, and that pulsing is obvious even to untrained ears. It is why a guitar can sound fine on its own and unmistakably wrong the moment a second instrument joins.

How a tuner hears pitch

A plucked string does not produce a single frequency. It produces a fundamental plus a stack of harmonics at two, three, four times that frequency and beyond, and on a guitar the harmonics are frequently louder than the fundamental. This is why the obvious approach — take the strongest frequency in the spectrum — fails badly, typically reporting a note an octave or a fifth above the one you actually played.

Better detectors work in the time domain instead, using autocorrelation. The idea is intuitive: slide a copy of the waveform against itself and look for the shift at which it lines up best with itself. A periodic signal correlates strongly with itself at a delay of exactly one period, so finding that delay gives you the period, and the fundamental frequency is simply the sample rate divided by it. Crucially it works on the shape of the whole waveform rather than on individual spectral peaks, so a weak fundamental buried under strong harmonics is still found correctly.

Two refinements do most of the remaining work. First, the correlation is normalised, so that its value does not simply decay as the shift grows — otherwise the algorithm biases toward reporting short periods, meaning high notes. Second, the detector takes the first strong peak rather than the tallest one. A signal that repeats every N samples also repeats every 2N and 3N samples, so a naive global maximum can land on a multiple of the true period and report a note an octave or two too low. Finally, since the true period rarely falls exactly on a whole number of samples, a parabola fitted through the peak and its two neighbours gives sub-sample precision — which is what turns a coarse estimate into a reading accurate to a couple of cents. Theguitar tunerruns exactly this pipeline on every animation frame, entirely inside your browser.

Tuning with a microphone, step by step

Start the tuner, allow microphone access, and pick your instrument and tuning from the dropdown. Then work one string at a time, thickest to thinnest. Pluck the string somewhere near the middle of its length with a moderate, even attack — hitting it hard makes the pitch briefly sharp as the extra tension takes a moment to settle, so the reading is most trustworthy a half-second after the pluck, while the note still rings clearly.

• Needle to the left (flat): the string is too loose. Tighten it.
• Needle to the right (sharp): the string is too tight. Loosen it past the target, then come back up.
• Green and locked: the note has held within five cents long enough to be real, not a lucky frame.

Always finish by tuning up to the note, never down to it. String tension is not evenly distributed: friction at the nut slot and the saddle means part of the string can sit at a different tension from the speaking length. Arriving from below leaves the whole string pulling against the tuning post, which is stable. Arriving from above leaves slack waiting to be pulled through the nut the first time you bend a note or strum hard, and the string drops flat exactly when you least want it to. If you overshoot, go clearly under and come back up rather than easing down.

Once all six are done, go around again. Every string you tighten adds a little tension to the neck, which pulls the others fractionally flat — a guitar that was badly out will need two or three full passes before it settles. If a string was very far off, expect to need a third pass, and check with a chord rather than only with the meter.

Tuning by ear when there is no mic

The classic method is the fifth-fret rule, and it is worth knowing because it works anywhere and trains your ear at the same time. Fret the sixth string at the fifth fret and it produces the same pitch as the open fifth string; match them. Fifth fret of the fifth string matches the open fourth, and fifth fret of the fourth matches the open third. Then comes the exception created by that major third: the fourth fret of the third string matches the open second string. Finally the fifth fret of the second string matches the open first.

Listen for beating rather than trying to judge the pitches directly. Play the two notes together and let them ring; if they are slightly apart you will hear a wobble in the loudness. Adjust until the wobble slows and disappears, and you are within a cent or two — far more precise than most people can manage by comparing pitches abstractly. The catch is that errors accumulate as you move up the strings, so anchor the sixth string to a known reference first. Tapping a string button in the tuner plays a clean reference tone for exactly this purpose.

The more accurate ear method uses harmonics. Lightly touch the sixth string directly over the fifth fret and pluck to get a bell-like harmonic; do the same over the seventh fret of the fifth string. Those two harmonics should be identical, and because they are pure sustained tones with little attack noise, the beating between them is extremely easy to hear. The pattern repeats up the guitar with the same third-string exception.

Why your guitar will not stay in tune

Assuming the instrument is not damaged, drifting tuning almost always comes from one of four causes, and all four are fixable.

New strings still stretching. Fresh strings creep for the first few hours of playing and will go flat repeatedly no matter how carefully you tune. Speed this up by gently pulling each string away from the fretboard along its length a few times, retuning after each pull, until the pitch stops dropping. Three or four cycles usually settles a set.

Binding at the nut. If tuning produces a faint ping and the pitch jumps rather than gliding, the string is catching in its slot and releasing in steps. A tiny amount of graphite from a pencil tip in the slot, or a purpose-made nut lubricant, fixes it immediately. This is by far the most common cause of a guitar that goes sharp after tuning and flat after the first big bend.

Temperature and humidity. Wood moves and metal expands. A guitar carried in from the cold will drift for ten or fifteen minutes as it equalises, which is why you tune after your instrument has settled in the room rather than the moment you open the case.

Winding and hardware. Two or three neat wraps down the post, each below the last, locks the string far better than a single wrap or a messy pile. On guitars with a tremolo, every string interacts with every other through the spring tension, so changing one moves the rest and several passes are mandatory.

The awkward truth: a perfectly tuned guitar is slightly out

Here is something that surprises most players. Even with all six open strings dead on, some chords will still sound slightly sour — and that is not your fault, your tuner's fault, or the guitar's fault. It is a consequence of equal temperament, the system that divides the octave into twelve mathematically identical steps so that every key is equally usable. The price of that universality is that no interval except the octave is acoustically pure. An equal-tempered major third is about 14 cents sharp of the naturally consonant ratio of 5:4, which is enough to hear as mild roughness in a big open chord.

A fretted instrument makes this more visible than a piano does, because you hear the same interval as an open-string dyad constantly. There are also physical contributions: pressing a string down stretches it slightly sharp, which is why guitars have adjustable saddles for intonation — setting the effective string length so the twelfth-fret note matches the twelfth-fret harmonic. If your open chords are fine but everything above the seventh fret sounds increasingly wrong, that is an intonation problem, not a tuning one, and no amount of retuning the open strings will fix it.

Some players work around temperament by using "sweetened" tunings, nudging the G and B strings a few cents to favour the chords they use most. It is a real technique, but it is a trade — improve one chord shape and you slightly worsen another. For nearly everyone the right answer is to tune accurately to equal temperament, get the intonation set properly, and accept the fourteen cents as the cost of being able to play in every key.

Alternate tunings worth knowing

Changing the open strings changes which chords fall naturally under the fingers, and that reshapes what you write. These are the ones that earn their place.

Drop D is the gentlest entry point: only the sixth string moves, everything else stays where you know it, and the bottom three strings become a power chord you can play with one finger anywhere on the neck. Half-step down changes no shapes at all — every chord you know still works, everything just sounds a semitone lower, which suits singers and gives a slightly looser string feel. Open G and DADGAD are bigger commitments that genuinely change your relationship with the instrument, because familiar shapes stop working and you have to find sounds by ear again. That disorientation is exactly why they are such reliable cures for writer's block.

Two practical cautions. Dropping strings a full tone or more lowers tension, which can leave the string floppy and buzzing against the frets; heavier gauges are usual for anything below Drop D. And a guitar with a floating tremolo will fight any tuning change, since altering one string's tension re-balances the whole bridge — expect several passes, or reserve alternate tunings for a fixed-bridge instrument.

Bass, ukulele and violin

A four-string bass is tuned E1 A1 D2 G2 — the same intervals as a guitar's bottom four strings, an octave lower. The low E sits at about 41 Hz, which is genuinely hard for small laptop and phone microphones to capture cleanly, so if readings jump around on the lowest string, try playing the twelfth-fret harmonic instead: it sounds an octave up, exactly in tune with the open string, and is far easier for a microphone to hear.

A soprano or concert ukulele in standard tuning is G4 C4 E4 A4, and the surprise there is that the fourth string is higher in pitch than the third. That is called re-entrant or "high G" tuning, and it is not a mistake — it gives the ukulele its characteristic bright, chiming sound, since strumming does not sweep from low to high. Some players fit a low-G string instead for a fuller range, which is why both variants exist in tuner presets.

A violin is tuned in fifths: G3 D4 A4 E5. Being fretless, its tuning matters differently — the open strings set the reference and the player adjusts every other note continuously by ear, often gravitating toward pure intervals rather than equal temperament. Violinists conventionally tune the A string first, matching an oboe or a reference tone, then tune the remaining strings in perfect fifths against it.

Why A = 440 Hz, and when it is not

The pitch of the note A above middle C is the anchor every other frequency is derived from, and it has not always been 440 Hz. Before standardisation, pitch varied enormously between cities and even between churches in the same city, with surviving instruments and tuning forks suggesting A anywhere from roughly 400 Hz to well above 450. Baroque ensembles today commonly settle on 415 Hz, almost exactly a semitone below modern pitch, which lets period instruments perform at something close to the tension they were designed for.

A = 440 Hz was adopted as an international standard in the mid-twentieth century, and it is what recordings, backing tracks, samples and other instruments assume. Even so, many orchestras tune slightly higher — 442 or 443 Hz is common in Europe — on the argument that a marginally brighter pitch projects better. If you are playing alone the reference is arbitrary, but the moment you play with anyone else or along to a recording, matching matters far more than the specific number. The tuner's reference slider covers 415 to 466 Hz so you can match whatever the room is doing.

Troubleshooting the reading

One more environmental note: the tuner deliberately disables the microphone's echo cancellation, noise suppression and automatic gain control. Those features exist to make speech clearer on calls, and every one of them distorts a sustained musical tone — noise suppression in particular treats a steady pitch as background hum and can attenuate it into nothing. If a different tuner behaves strangely, this is often why.

Build the habit

Tune every single time you pick the instrument up, before you play anything. It takes twenty seconds, and the alternative is worse than it sounds: practising on an out-of-tune guitar quietly teaches your ear that wrong intervals are correct, which is genuinely difficult to unlearn. Players who tune habitually develop noticeably better pitch discrimination, simply because everything they hear reinforces the right reference.

Check again after ten minutes of playing, especially with new strings or after bending. And finish with your ears rather than your eyes — play an open E chord, a D, and a G, and listen for roughness. The meter tells you each string is where it should be; the chord tells you whether the guitar sounds right, and that is the thing you were actually trying to achieve. When it does, open themetronomeand go and practise. You can come back to thetunerwhenever the chords start sounding rough again.