Lower tunings
From standard EADGBE, all the strings are down-tuned by the same degree of one semitone. Typically requires thicker gauge strings for two steps.
E♭/ D# tuning - E♭-A♭-D♭-G♭-B♭-E♭/ D#-G#-C#-F#-A#-D#
Half a step down from standard tuning.
D tuning - D-G-C-F-A-D
One full step down from standard tuning.
D♭/ C# tuning - D♭-G♭-B-E-A♭-D♭/ C#-F#-B-E-G#-C#
One and a half steps down.
C tuning - C-F-B♭-E♭-G-C / C-F-A#-D#-G-C
Two full steps down from normal tuning
B tuning - B-E-A-D-G♭-B / B-E-A-D-F#-B
Two and a half steps down from standard tuning.
B♭/ A# tuning - B♭-E♭-A♭-D♭-F-B♭/ A#-D#-G#-C#-E#-A#
Three full steps from standard tuning
A tuning - A-D-G-C-E-A
Three and a half steps down from standard tuning.
A♭/ G# tuning - A♭-D♭-G♭-B-E♭-A♭/ G#-C#-F#-B#-D#-G#
Four full steps down from standard tuning.
G tuning - G-C-F-B♭-D-G / G-C-F-A#-D-G
Four and a half steps down from standard tuning.
G♭/ F# tuning - G♭-B-E-A-D♭-G♭/ F#-B-E-A-C#-F#
Five full steps from standard tuning.
F tuning - F-B♭-E♭-A♭-C-F / F-A#-D#-G#-C-F
Five and one half steps down from standard tuning.
Octave Tuning - E-A-D-G-B-E
Six full steps (one octave) down from standard tuning. Essentially the same as standard tuning for a bass guitar.
Tunings as low as A tuning may be practiced on an unmodified instrument, although a baritone guitar is better-suited to avoid warping, as its neck and truss rod are designed for their tension. F and octave tuning are impractical for the standard guitar, since its scale is too short for a clear sound and unmodified tuners are not built to admit bass guitar gauge strings.
[edit]Higher tunings
From standard EADGBE, all the strings are tuned up by the same degree of one semitone. String tension will be higher. Typically requires thinner gauge strings, particularly the first string which could be as thin as six hundredths of an inch (about the thickness of a single human hair).
E high tuning -E-E-E-E-E-E
Strong E unison high string resonance(See E low tuning).
F tuning - F-B♭-E♭-A♭-C-F / F-C#-D#-G#-C-F
Half a step up from standard tuning.
G♭/ F# tuning - G♭-B-E-A-D♭-G♭/ F#-B-E-A-C#-F#
One full step up from standard.
G tuning also known as Terz tuning (sometimes spelled "Tierce", "Third", or "Tertz", all of which are acceptable) - G-C-F-B♭-D-G / G-C-F-A#-D-G
One and one half steps up from standard.
A♭/ G# tuning - A♭-D♭-G♭-B-E♭-A♭/ G#-C#-F#-B-D#-G#
Two full steps up from standard.
A tuning - A-D-G-C-E-A
Two and one half steps up from standard.
B♭/ A# tuning - B♭-E♭-A♭-D♭-F-B♭/ A#-D#-G#-C#-F-A#
Three full steps up from standard.
B tuning - B-E-A-D-G♭-B / B-E-A-D-F#-B
Three and one half steps up from standard.
[edit]Dropped tunings
These tunings have the 6th string tuned one full step below the other strings. Some of these may require a baritone guitar due to the extremely low notes. Others can be achieved using a capo and/or a partial capo.
Drop D - D-A-D-G-B-E
Standard tuning but with the 6th string dropped one full step.
Drop D♭/ Drop C# - D♭-A♭-D♭-G♭-B♭-E♭/ C#-G#-C#-F#-A#-D#
Same as Drop D, but every string is dropped one half step.
Drop C - C-G-C-F-A-D
One full step down from Drop D.
Drop B - B-G♭-B-E-A♭-D♭/ B-F#-B-E-G#-C#
One and one half steps down from Drop D.
Drop B♭/ Drop A# - B♭-F-B♭-E♭-G-C / A#-F-A#-D#-G-C
Two full steps down from Drop D.
Drop A - A-E-A-D-G♭-B / A-E-A-D-F#-B
Two and one half steps down from Drop D.
Drop A♭/ Drop G# - A♭-E♭-A♭-D♭-F-B♭/ G#-D#-G#-C#-F-A#
Three full steps down from Drop D.
Drop G - G-D-G-C-E-A
Three and one half steps down from Drop D.
Drop G♭/ Drop F# - G♭-D♭-G♭-B-E♭-A♭/ F#-C#-F#-B-D#-G#
Four full steps down from Drop D, or two full steps up from Drop D1.
Drop F - F-C-F-B♭-D-G / F-C-F-C#-D-G
Four and one half steps down from Drop D, or one and a half steps up from Drop D1.
Drop E - E-B-E-A-D♭-G♭/ E-B-E-A-C#-F#
Five full steps down from Drop D, or one full step up from Drop D1.
Drop E♭/ Drop D# - E♭-B♭-E♭-A♭-C-F / D#-A#-D#-G#-C-F
Five and one half steps down from Drop D, or one half step up from Drop D1.
Drop D1 Tuning - D-A-D-G-B-E
Six full steps (one octave) down from Drop D.
[edit]Double-dropped tunings
Similar to the dropped tunings, except that both the 1st and 6th strings are dropped one full step.
Drop D - D-A-D-G-B-D
Standard tuning but with the 1st and 6th string sdropped one full step.
Drop D♭/ Drop C# - D♭-A♭-D♭-G♭-B♭-D♭/ C#-G#-C#-F#-A#-C#
Same as Drop D, but every string is dropped one half step.
Drop C - C-G-C-F-A-C
One full step down from Drop D.
Drop B - B-G♭-B-E-A♭-B/ B-F#-B-E-G#-B
One and one half steps down from Drop D.
Drop B♭/ Drop A# - B♭-F-B♭-E♭-G-B♭ / A#-F-A#-D#-G-A#
Two full steps down from Drop D.
Drop A - A-E-A-D-G♭-A / A-E-A-D-F#-A
Two and one half steps down from Drop D.
Drop A♭/ Drop G# - A♭-E♭-A♭-D♭-F-A♭/ G#-D#-G#-C#-F-G#
Three full steps down from Drop D.
Drop G - G-D-G-C-E-G
Three and one half steps down from Drop D.
Drop G♭/ Drop F# - G♭-D♭-G♭-B-E♭-G♭/ F#-C#-F#-B-D#-F#
Four full steps down from Drop D, or two full steps up from Drop D1.
Drop F - F-C-F-B♭-D-F / F-C-F-C#-D-F
Four and one half steps down from Drop D, or one and a half steps up from Drop D1.
Drop E - E-B-E-A-D♭-E/ E-B-E-A-C#-E
Five full steps down from Drop D, or one full step up from Drop D1.
Drop E♭/ Drop D# - E♭-B♭-E♭-A♭-C-E♭ / D#-A#-D#-G#-C-D#
Five and one half steps down from Drop D, or one half step up from Drop D1.
Drop D1 Tuning - D-A-D-G-B-D
Six full steps (one octave) down from Drop D.