Tunings for the five string banjo

Standard tuning for a 5-string banjo is "G" tuning, which means that strumming all the strings "open", that is without fretting any of them, produces a G chord.

If you have a piano handy...

                     "Middle C"
                          |
                          V
           | # # | # # # | # # | # # # | # # | # # # |
           | # # | # # # | # # | # # # | # # | # # # |
           | # # | # # # | # # | # # # | # # | # # # |
           | | | | | | | | | | | | | | | | | | | | | |
          _|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_
              ^     ^   ^   ^     ^
              |     |   |   |     |
             4th   3rd 2nd 1st   5th String

              D     G   B   D     G

If you don't have a piano handy, but you've got a guitar that's tuned in the usual way, or you've got a pitch pipe meant for tuning guitars, the 2nd, 3rd, and 4th strings of the banjo are tuned the same as the 2nd, 3rd, and 4th strings of the guitar.

Once the 4th string is tuned, the 3rd string is tuned to the same pitch as the 4th string fretted at the 5th fret.

The 2nd string is tuned to the pitch of the 3rd string at the 4th fret.

The 1st string is tuned to the pitch of the 2nd string at the 3rd fret.

The 5th string is tuned to the pitch of the 1st string at the 5th fret.

Some other common tunings:

C tuning: From low to high: C, G, B, D, G

C tuning is the same as G tuning, except the 4th string is tuned down a whole step (two frets). So, the 3rd string will sound the same pitch as the 4th string fretted at the 7th fret.

D tuning: From low to high: D, F#, A, D, F#

The 4th string is tuned to the same D as in G tuning.

The 3rd string sounds as the 4th string at the 4th fret.

The 2nd string sounds as the 3rd string at the 3rd fret.

The 1st string sounds as the 2nd string at the 5th fret.

The 5th string sounds as the 1st string at the 4th fret.

The five string banjo is a folk instrument essentially, and so, like most folk instruments, it can be tuned and played many ways. A great many different tunings for the banjo have been devised. Even though this is the case, in modern times, banjo-pickers usually only play in the open G tuning, occasionally changing to D if they play bluegrass (though even that is becoming more and more uncommon) or C if they play in a more folk style, such as clawhammer.

I've tried to indicate which note each string makes in as simple a way as possible. The first letter corresponds to the fifth (or drone) string. It is represented by a lowercase letter. The drone is always in the octave two octaves above middle C. The other four are represented by capital letters. A letter with the number 1 after is in the octave above "middle C", a letter with 0 after is in the octave below.

G major, "open G", or "high bass" is by far the most common tuning. It's the tuning used in Bluegrass, and some folk songs. g D0 G0 B0 G1

C,"low bass," or "classic C" isn't quite as common, but is still widely used in folk music. Like Open G, it is a survival of an old tuning from the nineteenth century/minstral era, but up a whole fifth from the original. There are other tunings to play in the key of C, which at times are more practical, however this tuning has the advantage of being easy to switch into and out of if your banjo is normally tuned to G. It also shares the distinction of being one of the earlist konwn banjo tunings with open G. g C0 G0 B0 G1

"Double C" is a very popular tuning with clawhammer players. It is nearly the same as classic C, except that the B string has become a C. g C0 G0 C1 G1

"Mountain minor," "G-modal" or "Sawmill" is a variation on open G used in old folk songs of the Appalachians. The name is somewhat misleading, considering that it's actually a Gmaj6 chord, rather than being any sort of minor chord. g D0 G0 C(middle c) G1

D major (open D) is another folk tuning, occasionally heard in bluegrass. a (f# is also common) D0 F#0 A0 D1

G minor is yet another folk tuning. g D0 G0 Bb0 D1.

Open C was used by the legendary Uncle Dave Macon on many of his songs. It has several technical advantages over the normal C, however it is harder to tune into from open G. g (or a) C0 G1 C1 E1

sources:
http://zeppmusic.com/banjo/
How to Play the Five String Banjo by Pete Seeger
My own banjo-picking