Tuner for guitar, bass, ukulele and violin

String frequencies for every preset

At A4 = 440 Hz, in hertz, lowest string first (the order the tuner shows them). With A4 at 432 Hz every value is 432/440 of these, 1.8% or 31.8 cents lower: the A string of a guitar becomes 108 Hz.

The ukulele preset is the usual re-entrant tuning: the G string is G4, above the C4 next to it, not a low G3. The fretboard links open the chord finder with its guitar neck in that tuning, so a chord you play or tap there is named from the right notes.

How to tune a string

1. Pick the preset, press Start tuner and allow the microphone. Hold the instrument within about half a metre of the phone or laptop.
2. Play one open string, firmly, and let it ring. The string it is closest to lights up, and the line under the needle says how far off it is and which way to turn.
3. Tune up to the note from below. If a string is sharp, lower it past the note and bring it back up: the gear then holds the string under tension and it stays in tune longer.
4. Stop when the needle sits in the shaded middle and the note turns blue: within 3 cents. The note sounds a little sharp for the first fraction of a second after a hard pluck, so read it once the string has settled.
5. To check intonation, tune the open string, then fret the same string at the 12th fret: it should read the same note one octave up, at 0 cents. If it reads sharp, the saddle needs to move back; flat, forward.

How accurate is this

The page measures the time it takes the sound wave to repeat (the YIN method), not the loudest peak in a spectrum. It looks at the last 4,096 samples (85 ms at 48 kHz; 8,192 samples for bass, so the 32 ms period of a low B fits in more than twice), about 16 times a second. The needle shows the median of the last five readings with a short glide, so it does not jump on one bad frame, and settles in about half a second after a new string.

• On test tones (sine and sawtooth waves at 82.41, 110, 440 and 440 Hz + 15 cents, at 44.1 and 48 kHz), the test suite measures the error at under 0.1 cent. The display rounds to whole cents. Real strings are less steady than test tones, and we have not measured this tuner against a reference tuner on real instruments.
• A noisy room hurts. Fan noise and chatter do not repeat, so they make readings drop out rather than go wrong, but another instrument or a voice does repeat and can take over the reading. So can mains hum from an amplifier or a bad cable: it sits at 50 or 60 Hz (and multiples), right among a bass's low strings (E1 is 41.2 Hz, A1 is 55 Hz), so unplug or move away from humming gear when tuning low strings. Tune in a quiet room, one string at a time, with other strings muted.
• Phone and laptop microphones pick up little of a bass guitar's lowest notes: the fundamental of a low E is 41 Hz. The wave still repeats at 41 Hz even when the microphone only hears its overtones, so the tuner usually still reads E1. If it jumps an octave, the string name still tells you which string you are on.
• If the reading is steady but you think the result is wrong, check the A4 setting: it is 440 Hz unless you changed it.

What this page cannot do

• Tune several strings at once. Strum a chord and you get no reading or a wrong one; it hears one note at a time.
• Presets beyond these eight. The note, octave and cents read out any pitch from a fourth below the preset's lowest string up to 2 kHz, so any other tuning works note by note: for E♭ standard, tune each string to D#, G#, C#, F#, A#, D# at 0 cents.
• Tune a piano. Pianos are tuned with octaves slightly stretched, and this tuner uses exact equal temperament.
• Other temperaments or a reference outside A4 = 432 to 446 Hz.
• Work without microphone permission, or when another app is using the microphone.

Nothing is recorded or sent. The sound goes from the microphone into this page's memory, is measured and thrown away; nothing is saved, not even your preset. Stop turns the microphone off completely and the browser's recording indicator goes out. Apart from an anonymous page-view count, the page sends nothing anywhere. The microphone is opened with echo cancellation, noise suppression and automatic gain turned off, because those filters change the sound the tuner measures.

Play a chord and see its name on the on-screen piano or guitar, on a MIDI keyboard or into the microphone, or find the chords in every key.