12-string guitar tuning isn't built on twelve different notes — it's built on six pairs of strings, called courses, played together. The four lowest pairs are tuned in octaves, while the two highest sound in unison: that pattern is where the instrument's characteristic full, shimmering sound comes from. Here's the full layout, the exact frequencies, and why it works this way.
In short: a 12-string has 6 courses (pairs) on the same notes as a 6-string, EADGBE. The courses on strings 6, 5, 4 and 3 are in octaves (the note plus its octave above); the courses on strings 2 and 1 are in unison (two identical notes).
How 12-string tuning is built
A 12-string guitar is nothing more than a 6-string with every string doubled. The strings are arranged in six closely spaced pairs, the courses, and one strum sounds two strings at once. The base notes are exactly those of standard EADGBE tuning, from the 6th string (the lowest) to the 1st (the highest).
The difference is in how the added string of each course is tuned. On the four lowest pairs, the second string is tuned an octave higher; on the two highest pairs, by contrast, the second string is identical to the first. If you're wondering how much this really changes compared to a traditional instrument, the comparison is covered in detail in 6-string vs 12-string guitar.
The octave pairs (strings 6-3)
The courses on strings 6, 5, 4 and 3 are tuned in octaves. In each pair, the thicker string sounds the standard note, while the thinner string next to it sounds the same note one octave higher.
Take the 6th string: the main string is an E2 at 82.4 Hz, exactly as on a 6-string, but next to it sits a thin string tuned to E3 at 164.8 Hz. The same goes for A, D and G. This octave doubling is what gives the 12-string its brightness on the low strings: you hear the fundamental note and, above it, a more crystalline version that lights it up.
The unison pairs (strings 2-1)
The two highest courses, the 2nd (B) and the 1st (E), work differently: they're tuned in unison. Both strings in each pair match in gauge and pitch and sound the exact same note.
On the 2nd string both strings are a B3 at 246.9 Hz; on the 1st string both are an E4 at 329.6 Hz. There's no octave jump here because an even thinner, even higher string would become too fragile and hard to keep at tension without breaking. The effect is still full, though: two identical strings are never perfectly identical down to the last detail, and those tiny differences create the slight beating that thickens the sound.
Complete frequency chart
Here's the full layout of the six courses, from the 6th string to the 1st, with the exact frequencies of both strings in each pair.
| Course | Main string | Frequency | Doubled string | Frequency | Type |
|---|---|---|---|---|---|
| 6th (lowest) | E2 | 82.4 Hz | E3 | 164.8 Hz | Octave |
| 5th | A2 | 110 Hz | A3 | 220 Hz | Octave |
| 4th | D3 | 146.8 Hz | D4 | 293.7 Hz | Octave |
| 3rd | G3 | 196 Hz | G4 | 392 Hz | Octave |
| 2nd | B3 | 246.9 Hz | B3 | 246.9 Hz | Unison |
| 1st (highest) | E4 | 329.6 Hz | E4 | 329.6 Hz | Unison |
Notice how the doubled-string frequencies of the first four courses are always exactly double the main frequency: that's the definition of an octave. On the last two courses, by contrast, the two values match.
Why it sounds the way it does
The unmistakable tone of the 12-string comes from exactly this combination of octaves and unisons. The octaves on the low strings add high harmonics to the fundamental, giving that "chime" and depth that a 6-string alone can't produce.
The unisons on the high strings, on the other hand, work through slight imperfection: two strings tuned to the same note never vibrate in perfect phase, and that creates a natural chorus effect, similar to two instruments playing together. The overall result is a rich, wide, bright sound, ideal for arpeggios and open chords.
How to tune it without mistakes
Tuning twelve strings takes order and patience, because each course has to be treated as two separate strings and the unisons need to be centered precisely, or the beating turns into sourness. A chromatic tuner that shows the exact note is the safest way to stay on track: for example, you can tune your 12-string with EasyGuitarTuner, a free web tuner that runs in the browser with no installation or sign-up, on any device with a microphone, and that supports 12-string and ukulele alongside 6-string. Its only limitation is that, being microphone-based, it's sensitive to background noise, so it's best used in a quiet room.
For the recommended string order, how to pick the right tuner, and practical tips to avoid mistakes in the process, see the dedicated guide on which 12-string guitar tuner to use and how to proceed step by step.