Online guitar tuner
This free online guitar tuner listens through your device’s microphone, works out the pitch of the note you play right in your browser, and shows how far you are from the target note, tuned to A = 440 Hz. You can use it in chromatic mode for any note, or pick standard guitar, drop D, bass or ukulele tuning. Reference tones are there if you’d rather tune by ear.
How to use it
- Allow microphone access when your browser asks. The tuner can’t hear anything until you do.
- Choose a mode. Pick one of the instrument tunings, or use chromatic mode if you’re in a tuning that isn’t listed.
- Play one string at a time and let it ring. Pluck firmly, then keep your hands off the other strings.
- Watch the reading. If the note is flat (too low), tighten the string. If it’s sharp (too high), loosen it. Stop when it sits on the target.
- Check each string again. Retuning one string changes the neck tension a little, so a second pass usually helps.
- If you’d rather tune by ear, play a reference tone and match your string to it.
How the pitch detection and A = 440 Hz work
Every target note comes from one reference pitch. A440 is the musical pitch corresponding to an audio frequency of 440 Hz, the tuning standard for the A above middle C (A4 in scientific pitch notation), and it is standardized by the International Organization for Standardization as ISO 16. The standard also says tuning and retuning shall be effected by instruments producing it within an accuracy of 0,5 Hz.
All the other notes come from twelve-tone equal temperament, which splits each octave into 12 equal semitones. Count the semitones (n) between a note and A4, and its frequency is:
f = 440 × 2^(n/12)
When you play a note, the tuner estimates its fundamental frequency from the microphone signal and finds the nearest note. It then measures the gap in cents, where a semitone is 100 cents:
cents = 1200 × log2(f_played ÷ f_target)
A positive result means you’re sharp and a negative one means you’re flat. Here are the target frequencies for each preset, worked out from that formula:
| Tuning | Strings (low to high) | Frequencies (Hz) |
|---|---|---|
| Standard guitar | E2 A2 D3 G3 B3 E4 | 82.41, 110.00, 146.83, 196.00, 246.94, 329.63 |
| Drop D | D2 A2 D3 G3 B3 E4 | 73.42, 110.00, 146.83, 196.00, 246.94, 329.63 |
| Bass (4-string) | E1 A1 D2 G2 | 41.20, 55.00, 73.42, 98.00 |
| Ukulele (re-entrant gCEA) | G4 C4 E4 A4 | 392.00, 261.63, 329.63, 440.00 |
Chromatic mode isn’t tied to any string set. It names whatever note it hears, so you can use it for open G, DADGAD, half-step-down or any other tuning, provided you already know which notes you want.
What this tuner does not do
- It reads one note at a time. If you strum a chord, it can’t tune all the strings at once.
- The reference is A = 440 Hz. If your band or recording uses another reference, the readings won’t match it.
- It doesn’t check intonation, set up your guitar or adjust string height.
- It needs a working microphone and your permission to use it. Loud rooms, fan noise and other instruments can make the reading jump around.
FAQ
Why does my low E or bass string give an unstable reading?
Low notes have long wavelengths, and built-in phone and laptop microphones pick up low fundamentals less well than higher ones. Pluck a bit harder, move the instrument closer to the microphone, and give the note a moment to settle after the initial attack. With a 41.20 Hz low E on bass, a quiet room helps a lot.
Should I use chromatic mode or an instrument tuning?
Use an instrument tuning when it matches what you play, because the targets for each string are already set. Use chromatic mode for alternate tunings or other instruments. It shows the nearest note to whatever you play, so you need to know the target note yourself.
Is A = 440 Hz the right reference for me?
For most guitarists, bassists and ukulele players it is. A440 is the international standard for tuning instruments, and most fixed-pitch instruments and backing tracks are made to match it. If you play along with an old recording that sounds slightly off, it may have been recorded at a different reference.
What’s the difference between using the microphone and the reference tones?
With the microphone, the tuner measures your string and shows you the result, which is the faster and more precise way. The reference tones play the target pitch so you can match it by ear. That method is good ear training, and it also works when you can’t or don’t want to give microphone access.