The amount of possible combinations of GUIDs/UUIDs is so enormous that there are more possible combinations of GUIDs than there are grains of sand on planet Earth. To be more accurate, GUIDs are made from 128-bits. 2 bits are used for the variant and 4 bits are used for the version. That leaves 122 bits to be used to calculate a unique number. To calculate the number of combinations, use 2^122. That equals 5,316,911,983,139,663,491,615,228,241,121,400,000 possible combinations.