Instrument Tuner
Chromatic tuner using your microphone. Detect pitch, see nearest note, tune guitar, bass, ukulele, violin. Free online instrument tuner with cent deviation
A chromatic tuner converts the pitch your instrument is producing into the nearest musical note plus the deviation in cents (1/100th of a semitone). Hardware tuners cost $30-100; phone apps are free but often laggy. A browser tuner using Web Audio API + fast pitch-detection algorithms gets close to hardware accuracy in real time. This tuner identifies any pitch from a microphone, shows the nearest note (with octave) and deviation in cents, and supports alternate tunings (A=440 vs A=442 for some classical music).
How pitch detection works
- Microphone captures audio at 44.1 kHz or 48 kHz sample rate.
- Algorithm computes the fundamental frequency (f₀) — the lowest periodic component of the sound. Harmonics confuse naive FFT; modern tuners use autocorrelation, YIN, or MPM algorithms that are robust to harmonic-rich timbres.
- Frequency is converted to musical pitch: note = 12 · log₂(f / 440) + 69 (where 440 Hz is A4 = MIDI 69). Round to nearest integer for the note; fractional part × 100 = cents deviation.
- Display: note name (A4, B♭3, etc.) plus needle / bar showing cents deviation (-50 to +50).
Standard tunings and their math
- A4 = 440 Hz — international concert pitch since 1955 (ISO 16). Standard for almost all modern music.
- A4 = 442 Hz — some symphony orchestras in Europe (Berlin Philharmonic, Vienna Philharmonic) tune slightly higher; brighter sound.
- A4 = 415 Hz — Baroque pitch. About a semitone lower than modern. Used for "historically informed" early music performance.
- Equal temperament — 12 equal divisions of the octave (the modern default). Each semitone is the 12th root of 2 = 1.0594631...
- Just intonation — pure mathematical ratios (e.g., perfect fifth = 3:2 exactly). Sounds purer for individual intervals but cannot modulate between keys.
- Stretch tuning — pianos are tuned with octaves slightly wider than 2:1 to compensate for inharmonicity of real strings. Approximately 6 cents stretch at the extremes.
Working example
Input
Playing the open A string on a guitar; tuner shows 438 Hz
Output
Detected pitch: 438 Hz Nearest note: A4 (440 Hz) Deviation: -8 cents (slightly flat) Visual indicator: needle just left of center. Action: tighten the string slightly until the needle centers on A. A few turns of the tuning peg per cent; small adjustments — tuning pegs are sensitive. Reference frequencies for standard guitar tuning (E-A-D-G-B-E): E2 = 82.41 Hz A2 = 110.00 Hz D3 = 146.83 Hz G3 = 196.00 Hz B3 = 246.94 Hz E4 = 329.63 Hz
Acceptable tuning tolerance: ±5 cents for most music. ±2-3 cents for solo or chamber performance. ±0.5 cents for studio recording with multiple tracked instruments — overtones beat against each other audibly if instruments diverge.
Pitch-detection algorithms compared
- FFT-based peak detection — find the loudest frequency bin. Fast but confuses octaves on rich timbres (a low note with strong overtones gets reported as the overtone, an octave or fifth too high).
- Autocorrelation — find the lag at which the signal correlates with itself. Robust to harmonics. Computationally heavier.
- YIN — improvement on autocorrelation. Widely used in music applications. Good accuracy and speed.
- MPM (McLeod Pitch Method) — refined YIN. Very accurate; what modern browser tuners use.
- Neural network methods (CREPE, etc.) — best accuracy on noisy / harmonic-rich signals. Heavier to run; overkill for clean instrument tones.
When to reach for this tool
- You are tuning a guitar, bass, ukulele, violin, mandolin, or other pitch-variable instrument.
- You are tuning a brass or woodwind instrument and want to check intonation across the range.
- You are practicing pitch matching (singing in tune) and want feedback on each note.
- You are debugging an audio bug ("which note is this synthesizer actually playing?") and want a quick pitch reference.
What this tool will not do
- It will not tune polyphonic chords accurately. The algorithm detects the dominant fundamental; multi-note input produces unstable readings.
- It will not work in noisy environments. Background music, voices, fans bleed into the pitch detection. Use closer mic placement and quieter rooms.
- It will not replace a piano tuner. Real piano tuning involves stretched octaves, inharmonicity compensation, and trained-ear refinement. Software tuners get most strings approximately right; finishing needs a human.
- It will not record. For analyzing pitch over time (vibrato, pitch contour), use a DAW with a pitch-tracking plugin.
Frequently asked questions
Why does my tuner show octave-wrong notes?
FFT-based pitch detection sometimes locks onto a harmonic instead of the fundamental. Pluck firmly to emphasize the fundamental; mute strings you are not tuning; some tuners offer "string-specific" modes that constrain to the expected range.
What does "cents" mean?
1 cent = 1/100 of a semitone. There are 1200 cents in an octave. Human pitch discrimination is about 5 cents under ideal conditions. Two notes 50 cents apart sound clearly different (and bad together); 5 cents apart sound nearly the same.
Why is concert A 440 Hz?
Standardized internationally in 1955 (ISO 16). Before that, pitches varied across regions and over time — A could be anywhere from 415 to 466 Hz depending on era and locale. The 440 standard was a compromise. Some orchestras still use higher (442, 443) for brighter timbre.
How accurate is browser pitch detection?
Good. ±1-2 cents in clean conditions, comparable to hardware clip-on tuners. Limited by microphone quality and ambient noise. For high-precision work (studio recording), dedicated hardware tuners with direct-input cables still beat microphone-based methods.
Can I tune by ear?
Yes — by matching beats. Two strings near the same pitch produce audible beats (wow-wow-wow at the difference frequency). Eliminate beats = perfectly in tune. Slower beats = closer in pitch. This is how professional piano tuners work; takes practice to learn.
Why does my guitar go out of tune so fast?
New strings stretch over the first few hours of playing — tune frequently for the first day. After break-in, strings hold tune better. Temperature and humidity changes also shift pitch; for outdoor performance, retune after every 2-3 songs.
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Published · Updated · E-Utils editorial team