How to tune an instrument accurately with an online tuner
A tuner compares the pitch your instrument produces with the nearest target note and tells you how far off it is, measured in cents. One cent is one hundredth of a semitone, so 100 cents move you from one fret to the next.
This tuner listens through your microphone, estimates the fundamental frequency in real time and shows the result on a needle gauge, a strobe display or a scrolling pitch trace. Everything runs locally in your browser.
Tuning step by step
Pick your instrument and tuning, press Start tuner and play one open string at a time.
- Pluck the string firmly and let it ring; the first second after the attack is the least stable.
- If the needle sits left of centre the string is flat, so tighten it. Right of centre means sharp, so loosen it.
- Always finish by tightening up to the note rather than down from above; this keeps the string from slipping afterwards.
- Re-check every string once you have finished, because changing tension on one string shifts the others slightly.
Tap a string button to lock the target. Auto mode follows whichever string is closest to the pitch you play.
How the pitch is measured
The tuner uses the McLeod Pitch Method, a normalised autocorrelation algorithm that finds the period of the waveform rather than the loudest harmonic. This avoids the octave errors that simple spectrum peak pickers make on plucked strings, where the second harmonic can be louder than the fundamental.
The estimate is refined by interpolating between samples and then smoothed over several readings, with outliers rejected, so the display is steady without lagging behind a changing note.
Getting the most accurate reading
The software can resolve far less than a cent, so the real limits are acoustic.
- Tune in a quiet room and keep the microphone 10 to 30 cm from the instrument.
- Play one note at a time; chords and ringing sympathetic strings confuse any tuner.
- Lower the input sensitivity in a noisy room, or raise it if soft notes are ignored.
- Set the reference pitch to match whoever you play with: 440 Hz is standard, 415 Hz is common for baroque ensembles and some orchestras use 442 Hz.
On a phone, choose the Needle view for coarse tuning and the Strobe view for the final few cents.
Use the reference tone to tune by ear, compare notes with the Frequency to Note converter, or look at your instrument's overtones with the Spectrum Analyzer.