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Open C tuner: C G C G C E, free, with your mic

This is a free online guitar tuner, already set to Open C. The strings become C G C G C E, and the six open strings sound a deep C major chord. Press Start, play one string on its own, let the note settle, then aim for 0 cents. The tuner widens its analysis window on this preset, because the low C is a slow wave. No account, no download. It sits alongside the rest of our free guitar tools.

What Open C tuning is

Open C is an open tuning: C G C G C E, from the thickest string to the thinnest. Strum the open strings and you hear a C major chord, with three Cs, two Gs and one E spread over several octaves. That gives a lot of low end, open strings that keep ringing, and a color that suits fingerstyle, slide and modern textures.

Written with octaves, the six strings are C2 G2 C3 G3 C4 E4. The letter is the note, the number is the octave: C2 is the low C of the sixth string, two octaves under C4. E4 is simply the first string, which stays on the E of standard tuning.

Three different things carry the letter C on a guitar, and it pays to keep them apart. The C chord, played X 3 2 0 1 0 in standard tuning. The Open C tuning, the subject of this page. And C standard, C F Bb Eb G C, which is standard tuning taken down two whole steps and has its own C standard tuner.

A few reference points to listen to. John Butler Trio, Ocean, is the classic example of wide fingerstyle in Open C. Led Zeppelin, Friends, is tuned C A C G C E, a variant with an A on the fifth string that leans toward Open C6. Soundgarden, Burden in My Hand, uses a rockier variant of Open C with a heavy low end, and Devin Townsend uses Open C on many songs, electric and massive. The same tuning can sound acoustic, orchestral, folk or close to post-rock, depending on the tempo, the strings and how many open strings you let ring.

How to tune to Open C from standard

Open C is mostly about taking the low strings down. The only string that goes up is the second, from B to C. Work slowly, especially if your strings are old or already under a lot of tension.

String Standard Open C Move Target, at A 440
Sixth, the thickest E2 C2 down two whole steps 65.41 Hz
Fifth A2 G2 down one whole step 98.00 Hz
Fourth D3 C3 down one whole step 130.81 Hz
Third G3 G3 unchanged 196.00 Hz
Second B3 C4 up a half step 261.63 Hz
First, the thinnest E4 E4 unchanged 329.63 Hz

Reference tones, A4 = 440 Hz

One button per string in Open C, from the low C up to the E on top. Play the string on the guitar and bring it to the same pitch.

Each tone is synthesized by your browser at the exact frequency, with A4 at 440 Hz as the reference, so it stands in for a tuning fork. No audio file is downloaded.

  1. Go round all six strings once, roughly. Three strings are losing tension, and each one you loosen changes the pull on the others.
  2. Go round a second time, properly, aiming for 0 cents. Strings that have come down a long way rarely settle on the first pass, the sixth string above all, since it drops from E to C.
  3. Bring the second string up to C last, gently. It is the only one going up, and it is easier to land on the note from below.
  4. Strum the open strings. You should hear a clean C major chord. If one note sticks out, read it on the tuner rather than guessing which.
Why the reading takes a moment on the low C: at 440 Hz that string is 65.41 Hz, and the usual analysis window is too short to see enough of it. Measured on a synthetic signal, the low C came out 17 cents away from its target with the usual window, and about 2.5 cents with the wider one this preset loads. Let the string ring instead of tapping at it.

Easy chords in Open C

The immediate appeal of Open C is that major chords become very easy to read: one full barre gives you a major chord. Fret 0 is C, fret 2 is D, fret 5 is F and fret 7 is G. The shapes are written from the sixth string to the first.

Chord Shape How
C 000000 All six strings open.
D 222222 Full barre at the 2nd fret.
E 444444 Full barre at the 4th fret.
F 555555 Full barre at the 5th fret.
G 777777 Full barre at the 7th fret.
Am7 x20000 A simple minor color against the open strings.

Open C changes the shapes, not the logic: you still need to know which notes make up the chord. If shapes on a diagram are new to you, how to read chord diagrams explains the grid in a few minutes.

Open C, C standard, Open C6: the differences

Open C does not mean C standard. Both start on a low C, but they serve different kinds of playing.

Tuning Notes Sound Natural use
Open C C G C G C E An open C major chord, low and wide. Fingerstyle, drones, slide, modern folk.
C standard C F Bb Eb G C Standard tuning taken down two whole steps. Low rock and metal, with the usual shapes kept.
Open C6 C A C G C E A sixth chord color, closer to jazz and lap steel. Slide, Hawaiian, swing.
DADGAD D A D G A D Modal, neither major nor minor. Celtic, modal fingerstyle, drones.

The other widespread open major tuning is Open G, D G D G B D, with its own Open G tuner. For a more modal color, the DADGAD tuner and the Open D tuner open straight onto those two.

String gauges and tension in Open C

The sixth string drops from E to C, so a set that is too light can turn vague in the low end. On an acoustic, a common starting point is 12-54, or 13-56 if you attack hard. On an electric, it depends on your scale length and your touch.

The right gauge is not a matter of level. It depends on the instrument, your picking hand, the scale length and the sound you are after. The string gauge chart for drop and low tunings goes through it tuning by tuning.

A ten minute practice plan

  1. Tune. Set each string with the tuner, then go round a second time.
  2. Listen to the C major. Strum the open strings and pick out the C, the G and the E in the ringing.
  3. Try the barres. Move a full barre to frets 2, 5 and 7 to feel how the major chords line up.
  4. Add rhythm. Work slowly with the online metronome, so the sustain does not hide a string that has drifted.

Frequently asked questions

How do I tune my guitar to Open C?
From standard tuning, set the strings to C G C G C E, from the sixth string to the first. The sixth, fifth and fourth strings go down, the third and first stay where they are, and the second goes up a half step, from B to C. This tuner opens on Open C, so it shows you those six targets directly.
Is Open C the same as C standard?
No. Open C gives you a C major chord on the open strings: C G C G C E. C standard keeps the intervals of standard tuning and moves everything two whole steps down: C F Bb Eb G C. Both have their own preset in the menu, and C standard has its own C standard tuner page.
What is the difference between the C chord and Open C?
The C chord is C major, played X 3 2 0 1 0 in standard tuning. Open C is a tuning: C G C G C E. Once the guitar is in Open C, the C chord is simply the six open strings.
What do C2 and E4 mean?
They are note names with their octave. C2 is the low C of the sixth string, 65.41 Hz. E4 is the E of the first string, 329.63 Hz, the same note as in standard tuning. Some chord books also write C2 for a chord, a C with the second (D) added, which is close to Csus2 and has nothing to do with the sixth string.
Which easy chords can I play in Open C?
Full barres give major chords: 000000 for C, 222222 for D, 555555 for F and 777777 for G. Then let some open strings ring against them to add color.
Do I need different strings for Open C?
Often, if the low strings turn floppy. On an acoustic, 12-54 is a common starting point, or 13-56 if you play hard. The right set depends on your guitar and your touch more than on any rule. The string gauge chart by tuning covers it in detail.
Yohann Abbou, guitar teacher and founder of Guitar Social Club

Who made this

Guitar Social Club is the work of Yohann Abbou, a guitar teacher in Paris. He teaches adults: people with jobs, limited practice time and a clear idea of the songs they want to play. The tools come out of his lessons, which is why none of them asks you to sign up before it works, and why this one shows you cents rather than a green light. The rest of our free guitar tools work the same way.

More about Yohann on his page, and about why Guitar Social Club exists.