Guitar Tuner

Tune a six-string guitar three ways: let the live tuner listen through your microphone and show how many cents each string is off, play exact reference tones and tune by ear, or check a recording of a string. Seven tunings are built in, and the reference pitch can be moved from A4 = 440 Hz to 432, 442 or anything between 400 and 480 Hz. The sound is analysed in your browser and never recorded or sent anywhere.

How to use this tool

1. Choose the mode and the tuning (Standard is E A D G B E).
2. Live tuning: press Calculate, allow the microphone, then pluck one string at a time and turn the peg until the bar is centred and green.
3. By ear: press Calculate, play each reference tone and match the string to it.
4. Recording: choose "Check a recording", pick a short recording of one string and press Calculate.

Formula

f = A4 × 2^((n − 69) ÷ 12) · cents = 1200 × log2(f_played ÷ f_target)

n is the MIDI note number (A4 = 69, low E = 40). The pitch is found with the YIN method: it compares the sound with delayed copies of itself, takes the delay with the best match as the period, and refines it between samples. A string within ±5 cents is shown as in tune; 100 cents is one semitone.

Example

In standard tuning the low E string should be 440 × 2^((40 − 69) ÷ 12) = 82.41 Hz. If the tuner hears 81.5 Hz, that is 1200 × log2(81.5 ÷ 82.41) = −19 cents: flat, so tighten the string a little.