To store the geocaches in the geocaching.com database, each geocache is assigned a unique number. To save space, this number is encoded in GC codes.
GC codes meanwhile consist of the 31 characters 0, 1, 2, 3, 4,5 6, 7, 8, 9, A, B, C, D,E F, G, H, J, K, M, N, P, Q, R, T, V, W, X, Y and Z.
The conversion is done on the basis of 31.