Tuning guitar using harmonics is useful for fine tuning after you've tuned by comparing strings, or if you have poor intonation caused by high string height.
If your guitar has intonation problems, it won't tune up 100% without a repair or adjustment, but, tuning with harmonics will make it more bearable until then.
If you're a beginner you may wish to skip this page for now.
How to Play a Harmonic on a Guitar
A harmonic has a bell-like ring. Natural harmonics occur at the 5th, 7th, and 12th frets. When tuning guitar using harmonics you only use the harmonics at the 5th and 7th frets.
Place your fretting finger directly above the fret, not behind the fret. Touch the string lightly above the fret(5th, 7th, or 12th) and lift your finger off about the same time as you pluck the string with your pick or finger. Don't press the string all the way down to the fretboard.
You are aiming for a bright ringing tone. Keep trying until it happens, it takes a bit of practice. Once you can play a harmonic, you can tune your guitar by the doing the following:
You will need an A440 tuning fork or use the online tuning fork, which will open in a new window, and can be resized and moved to the right side of the page.
Next, play a harmonic at the A string, 5th fret. Tune it to the harmonic at the D string, 7th fret.
Next, play a harmonic on the E string, 5th fret and tune that to the harmonic on the A string, 7th fret. Tune the low E, and A strings accurately because you'll tune the high E string and B string to the low E string.
Next, tune the open high E string, to the harmonic on the low E string, 5th fret.
Next, tune the open B string to the harmonic on the low E string, 7th fret.
Finally, tune the G string, 5th fret, to the harmonic on the B string,7th fret, or for a guitar with intonation problems, you can also try fretting the G string normally, and compare the 4th fret to the open B string. Try tuning the G string by using both methods, to see which works best.